International Journal of Modern Physics B

The status of Mg alloy application, and then some key issues limiting their applications and the corresponding accesses were briefly discussed. It was supposed that development of new alloys with high performance and low cost, investigating advanced forming technology, and development of credible and effective surface modification technologies and related equipment were the urgent tasks in present. Correspondingly, three aspects of researches were carried out. (1) A new alloy with high strength and elongation, but low RE and Zn contents, named ZW21, was invented. (2) Semisolid ingots of AZ91D, AM60 and ZW21 alloys available for thixoforming were prepared. Thixoforming increased the ultimate tensile strength of AZ91D alloy by 20% compared with permanent mould casting. (3) A new kind of micro arc oxidation equipment with a capacity of treating 6m² surface was developed and has been used to treating motorcycle hub of magnesium alloy.

This study investigated on thermal deformation of AC4C aluminum alloy casting material for tire mold built in metal casting method. In this study, temperature, displacement and stress distributions of AC4C casting material occurred inside the mold were numerically calculated by finite element analysis (FEA). Also, temperature profiles of AC4C were experimentally measured to investigate the temperature characteristics during the solidification process in metal casting device. The result of this study revealed that the numerical result of temperature profiles predicted a rapid cooling from initial state to about 25 minutes, but the experimental result of it uniformly occurred from initial state to about 15 minutes by the phase change. However, the cooling patterns of two cases were almost similar results in the whole cooling process. Also, thermal deformation was generated by the difference of cooling temperature between the surface and inside of the casting from the results of displacement and stress distribution predicted by FEA.

In this study, constitutional liquation in AZ91 cast alloy at 440°C and 465°C was experimentally simulated. Metallurgical examination was conducted to reveal the morphology of the constitutional liquid and dihedral angle was measured to evaluate the wettability of the liquid on grain boundary. Dihedral angle was found to be initially ~30 degree and thus grain boundaries were incomplete wet. During annealing, the metastable constitutional liquid resolidified, followed by grain growth. The extent of grain boundary wetting by the remaining liquid increased slightly with treating time. The rate of resolidification was also evaluated and the factors affecting this rate were discussed.

The magnesium silicide precipitates in the 6XXX series alloy are the main components contributing to the heat treatable properties and T6 strength of the alloy, which is influenced by the size, morphology and distribution of this phase. During the extrusion process, the strength contributing phase, magnesium silicide is supposed to dissolve and form again in a controlled state during age hardening. Whereas the intermetallic AlFeSi phase has little if any influence on the strength, the β phase of this intermetallic is known to cause brittle fracture of this alloy, as opposed to the less detrimental, more equiaxed α phase formed during homogenisation.

This study investigates the as-extruded 6060 and the more heavily alloyed 6261 aluminium alloys, as well as the subsequent heat treated forms to investigate the ageing conditions to optimise hardening and shorten age hardening times for higher cost effectiveness. The microstructure, texture and precipitate size and distributions were studied using optical microscopy, SEM, EBSD and DSC. SEM and EDAX results have indicated signs of evenly distributed α AlFeSi and β Magnesium Silicide precipitates. The phase responsible for hardening is believed to be the much smaller scaled β" magnesium silicide, requiring much higher resolution studies.

The corrosion morphology and electrochemical behavior of 5A06 aluminum alloy and SiC_p/ 5A06 aluminum matrix composite (MMC), were investigated by means of the immersion test and various electrochemical techniques. The surface morphology of the samples tested was observed by optical (OM) and scanning electron microscopy (SEM) accompanied with energy dispersion spectroscopy (EDS) to reveal the damage caused by the immersion. It was found that the composite corroded faster than the matrix alloy due to the presence of fine and uniformly distributed intermetallics and crevices at the SiC_p/ matrix interface, rather than galvanic corrosion between SiC_p and the matrix phase. Cyclic potentiodynamic polarization (CV) and the variation of the open circuit potential with time (E_corr-t) were carried out and revealed similar corrosion potential (E_corr) and pitting potential (E_pit) for the composite and the matrix alloy. More pitting initiation sites were recorded on the composite surface, in accordance with its greater electronegative protection potential (E_prot).

Dynamic failure behaviors of the extruded Mg-12Gd-3Y-0.4Zr alloy were investigated by means of optical microscope and scanning electron microscope (SEM). The dynamic tensile and compressive tests were carried out at 423K~798K and strain rates of 10²~10³s^-1 using a split Hopkinson pressure bar. Additionally, in order to study the failure characteristic of this alloy at higher strain rates, such as 10⁷s^-1, a series of ballistic tests were carried out. The results indicate that the failure mechanisms of both tensile and compressive specimens exhibit an obvious dependence on the temperature. As the testing temperatures increased from 423K to 798K, the fractographs of the tensile specimens varied from quasi-cleavage fracture to intergranular rupture, and the failure modes of the compressive specimens changed from shear cracks to dynamic recrystallization zone. Adiabatic shear bands with an average width 10µm were observed in the post-test magnesium targets penetrated by steel balls.

Aluminium has good corrosion properties and a high strength to weight reduction which makes it favourable in many applications. The increased use of aluminium casting in the automotive industry does also imply that the need for design data for aluminium increases. Especially for castings, the influences of casting defects are always an issue. For this reason fatigue properties for as-cast sand and permanent mould specimens with different contents of porosity have been studied. The cast aluminium specimens of two different porosities were fatigue tested in cyclic axial test at R=-1. Prior to fatigue test specimens were examined by CT-scan and sorted into two quality groups depending on the porosity level.

The aim of this work was to investigate the fatigue life for cast AC4C-T6 alloy with different amounts of inherent porosity. An additional aim was to predict the durability for cast components with defect constrained in a specified volume of components, by using a commercial program MSC. Fatigue.

Microstructure stability in fully lamellar (FL) structure TiAl based intermatellics have been studied. The experiment results have shown that the smaller the lamellar spacing is, the more instable the lamellar structure is. The distinct lamellar spheroidization occurs at 1150°C holding for 24h. This phenomena may be caused by lamellar coarsening and decomposition. The linear residual β phase distributed in the Ti-47A1-2Cr-2Nb alloy may prevent lamellar spheroidization and improves the stability of lamellar structure significantly.

A bulk and dense nc Ni-24.7% Co with an average grain size of 15nm was fabricated by a direct current electrodeposition. This Ni-24.7%Co exhibits very high tensile strength of 1813MPa to 2232MPa with relatively good tensile ductility of 6.0%~9.6% under tensile test over a wide strain rate range of 0.417s^-1 ~ 1.35×10^-5s^-1. The combination of high strength and good ductility should be attributed to the increased strain hardening ability induced by the addition of alloying Co element. The interaction of dislocation and grain boundaries is the rate-controlling deformation mechanism controlled in the Ni-24.7%Co based on its high strain rate sensitivity of 0.029 and small activity volume of ~14b³.

Nanosheets of cobalt and nickel hydroxides nanosheets were prepared by delamination of layered compounds, Co^II(OH)_1.73(DBS)_0.27·0.87H₂O (Co-DBS, DBS = dodecylbenzene sulfonate) and Ni^II(OH)_1.63(DBS)_0.37·1.24H₂O (Ni-DBS), respectively. Powder X-ray diffraction analyses of the layered compounds revealed lattice parameters of a₀ = 3.07 Å and c₀ = 30 Å (Co-DBS) and a₀ = 3.09 Å and c₀ = 30 Å (Ni-DBS) in the hexagonal system. Dispersions of Co-DBS and Ni-DBS in 1-butanol produced colloidal solutions of nanosheets, [Co-DBS]_delam and [Ni-DBS]_delam, respectively. Poly(vinylpyrrolidone) (PVP) was dissolved in [Co-DBS]_delam and [Ni-DBS]_delam and the mixtures were dried to yield Co-PVP and Ni-PVP, respectively. These nanosheets measured 150-500 nm for [Co-DBS]_delam and 135-400 nm for [Ni-DBS]_delam by means of dynamic light scattering. Atomic force microscopy images showed lateral dimensions of 100-500 nm for [Co-DBS]_delam and 50-100 nm for [Ni-DBS]_delam. In the former image, the cobalt hydroxide nanosheets had a fairly flat terrace structure with thickness of 3.1-3.6 nm and with aspect ratios of 30-150, whereas in the latter image dome-like nanosheets of nickel hydroxide with height of 2.2-2.3 nm were confirmed. These nanosheets were regarded as monolayer. Magnetization experiments at 1.8 K showed hysteresis loops for Co-DBS, Co-PVP, Ni-DBS, and Ni-PVP.

Based on the consideration on size-dependent temperature T_m(D) where D denotes the diameter of nanoparticles and nanowires or the thickness of thin films, the size-dependent band-gap ΔE_g(D) and dielectric constant ε(D) of low dimensional materials are modeled without any adjustable parameter. The model predicts an increase of the band-gap and a decrease of dielectric constant with drop of Si nanocrystals' size. The predicted results correspond to experimental and computer simulation results of Si nanocrystals.

FeNi nanowire arrays were fabricated into the pores of porous alumina template by a simple alternating current electrodeposition method in this work. FeNi nanowires with different diameters were obtained depending on the pore size arrangement of alumina templates. FeNi nanowire arrays exhibited obviously magnetic anisotropy, and the easy axis was along the nanowires. When the applied magnetic field was parallel to the nanowires, the coercivity (H_c) and the maximum remnant ratio (M_r/M_s) are considerable higher than those while the magnetic field perpendicular to the nanowires. FeNi nanowires prepared in this work are expected to be utilized as the perpendicular magnetic recording media. The magnetic domain structure and the magnetizing mechanism of FeNi nanowires were also been discussed.

Nanostructured Cu-(2.5-10vol.%)Al₂O₃ nanocomposites were produced using high energy mechanical milling. For the as-milled Cu-Al₂O₃ composite powder particles having Al₂O₃ volume fractions of 2.5% and 5%, the increase in average microhardness is significant with the increase of milling time from 12 hours to 24 hours. With the increase of the content of Al₂O₃ nanoparticles the microhardness increases and in the range of 255HV-270HV. The milled nanocomposite powders were heat treated at 150, 300, 400 and 500°C for 1 hour, respectively, to determine the thermal stability of the powder particles as a function of annealing temperature. The average microhardness increased/decreased for the Cu-Al₂O₃ composites after annealing at 150°C due to the dislocation density, while increasing the annealing temperature to 300°C and 400°C the average microhardness almost remained mostly unchanged. Further increasing the annealing temperature to 500°C causes significant decrease in average microhardness due to reduction in dislocation density and coarsening of Cu grains of the Cu-Al₂O₃ composite powders produced after 24 hours of milling. This paper is to report and discuss the changes of the microhardness of the material, caused by the compositions and processing conditions, used to fabricate the Cu-(2.5-10)vol.%Al₂O₃ nanocomposite powders.

The effect of alloy composition on improving glass-forming ability of La-based alloys is investigated in this work. Previous composition criteria demonstrated that the alloys with high glass-forming ability should have negative heats of mixing among the main constituent elements. In this study, the addition of Fe to a La-based La-Al-Ni-Cu alloy significantly improved the glass-forming ability, although the heat of mixing between Fe and the main element La is positive. La-Al-Ni-Cu-Fe bulk metallic glasses with diameters up to 15 mm were prepared by the method of pouring the molten alloys into a copper mold. These La-Al-Ni-Cu-Fe bulk metallic glasses exhibit relatively wide supercooled liquid region of about 50 k, and high T_rg(T_g/T_l) and γ(T_x/(T_g+T_l)) values. It is found that the addition of Fe to the La-Al-Ni-Cu alloy lowers the Gibbs free energy difference between the liquid and crystalline phases in the supercooled liquid region and enhances the glass-forming ability of the alloy.

Structural relaxation by isothermal annealing below the glass transition temperature is conducted on a Zr_64.13Cu_15.75Ni_10.12Al₁₀ bulk metallic glass. The effect of structural relaxation on thermal and mechanical properties was investigated by differential scanning calorimetry and instrumented nanoindentation. The recovery of the enthalpy in the DSC curves indicates that thermally unstable defects were annihilated through structural relaxation. During nanoindentation, the structural relaxation did not have a significant influence on the serrated plastic flow behavior. However, Structural relaxation shows an obvious effect in increasing both the hardness and elastic modulus, which is attributed to the annihilation of thermally unstable defects that resulted from the relaxation.

Ti-based bulk metallic glasses (BMGs) have great potential for use as structural materials due to their excellent mechanical properties. How to fabricate Ti-based metallic glasses with sufficient large size has always been the key issue in both the theoretic and technology aspects since finding the BMG. In this paper, we try to fabricate Ti-based metallic glasses with high glass-forming ability (GFA) through composition design based on various empirical ideas. BMG alloy with composition of Ti_43.89Cu_43.60Zr_6.75Ni_5.76 was synthesized based on the deep eutectic idea, and the critical diameter of this glassy alloy reaches to 2 mm. The GFA of this alloy was further improved by small addition of Si (0.5-1 at %). BMG rods with diameters up to 3mm were synthesized for compositions of Ti_42.89Cu_43.60Zr_6.75Ni_5.76Si₁, Ti_43.89Cu_43.60Zr_6.25Ni_5.76Si_0.5 and Ti_43.89Cu_43.60Zr_6.75Ni_4.76Si₁. The amorphous structure of all the samples was confirmed by X-ray diffraction (XRD) method. The thermal stability associated with glass transition, supercooled liquid region and crystallization was investigated by differential scanning calorimetry (DSC). Possible mechanisms for the improvement of GFA were discussed.

Formation of icosahedral clusters in Ni_66.7Zr_33.3 alloy during rapid solidification is studied with molecular dynamics simulations. It is found that the growth rate of the smallest icosahedral cluster (Ih13) in Ni_66.7Zr_33.3 alloy reaches its maximum at glass transition temperature region. The Ih13 in Ni_66.7Zr_33.3 alloy contain the retained from the higher temperatures and the new grown, which reach its maximum at about 900K as well as the new grown vertex atoms of Ih13. The ratio of new grown center atoms to the new grown vertex atoms increases with decreasing temperatures, which implies that the new Ih13 form beside original Ih13 and the icosahedral clusters coalesce to the larger ones during solidification. The stabilities of center atoms and vertex atoms of Ih13 increase with decreasing temperatures, and the stability of the center atoms becomes larger than that of vertex atoms blow 900K because of its rapid increase at glass transition temperatures. The results show that the evolutions of atomic arrangement during cooling change abruptly at glass transition region.

The objective of this work is to investigate the influence of electromechanical cyclic loading on the performance of a bending piezoelectric composite actuator. We have analyzed the fatigue damage mechanisms in terms of the behavior of the AE event rate. It was found that whether the actuators are subjected to purely electric loading or electromechanical loading, the initial fatigue damage of the bending piezoelectric composite actuator was caused by the transgranular fracture in the PZT ceramic layer; the final failure was caused only in the case of PCAWB under electromechanical loading by a local discharge, which critically affected the performance reduction of the actuators. As the number of cycles increased, a large reduction in displacement performance coincided with a high AE event rate, which was identified via microscopic observations.

Optical switch prototypes are developed based on the new concept that the input fiber is directly moved by the deflection of a piezoelectric tube actuator. The piezoelectric tube actuators used in the switch prototypes are manufactured by an electrophoretic deposition process. The tubes are low cost and compact in size with an inner diameter of less than 1mm. They have a deflection of 65 µm which is adequate to actuate the input fiber for switching.

A number of multimode 1×2 fiber optical switch prototypes have previously been built. To develop the new 1×4 optical switch, a new output fiber alignment device was fabricated. The conductive coating on the piezoelectric tube actuator was sectored into four. Also, the power supply unit was redesigned in order to provide high voltage for the four-sectored tube. The success in the 1×4 prototype development proves that the new multiple-output piezoelectric switching concept is feasible. The concept demonstrates an advantage over some other opto-mechanical switches which need to be cascaded to achieve a multiple-output configuration.

Smart materials can be defined as materials that sense and react to environmental conditions or stimuli. In recent years, a wide range of novel smart materials have been developed in biomaterials, sensors, actuators, etc. Their applications cover aerospace, automobile, telecommunications, etc. This paper presents some recent progresses in polymeric smart materials. Special emphasis is laid upon electroactive polymer (EAP), shape memory polymer (SMP) and their composites. For the electroactive polymer, an analysis of stability of dielectric elastomer using strain energy function is derived, and one type of electroactive polymer actuator is presented. For the shape memory polymer, a new method is developed to use infrared laser to actuate the SMP through the optical fiber embedded within the SMP. Electrically conductive nanocarbon powders are utilized as the fillers to improve the electrical conductivity of polymer. A series of fundamental investigations of electroactive SMP are performed and the shape recovery is demonstrated.

Ti-TiC-TiC/DLC gradient nano-composite films have been prepared on the NiTi substrates by the technique of plasma immersion ion implantation and deposition (PIIID) combining with plasma-enhanced chemical vapor deposition (PECVD). The influence of C₂H₂ flow rate ranging from 30sccm to 50sccm on the chemical structure, microstructure, mechanical properties and corrosion resistance of resulting thin films are investigated by XPS, XRD, friction coefficient test, nano-indentation, electrochemical corrosion test and atomic absorption spectrometry. XPS and XRD results indicate that on the outmost layer, the Ti ions are mixed with the DLC film and form TiC phase, the binding energy of C 1s and the composition concentration of TiC depend heavily on the C₂H₂ flow rate. With the increase of C₂H₂ flow rate, the content of TiC and the ratio of carbon sp³/sp² decreases. The nano-indentation and friction experiments indicate that the gradient composite film at 30 sccm has a higher hardness and lower friction coefficient compared with that of the bare TiNi alloy. The microscratch curve tests indicate that Ti-TiC-TiC/DLC gradient composite films have an excellent bonding property with the substrate. Based on the electrochemical measurement and ion releasing tests, we have found that the Ti-TiC-TiC/DLC gradient composite films exhibit better corrosion resistance property and higher depression ability for the Ni ion releasing from the NiTi substrate in the Hank's solution at 37°C.

Fe-Ni-Co-Ti alloys have been concerned as a potential magnetically induced shape memory alloy (MISMA) with high output power and low cost. Thin plate martensite with twin substructure, which is the key to get MISME, can be preserved at room temperature only after appropriate heat treatment in a certain composition range. Precipitation transformation in Fe-Ni-Co-Ti alloy was investigated by means of electrical resistivity and stress relaxation methods in this paper. Kinetics of precipitation was also discussed with JMA Equation.

The effect of Fe elements on the total energy of Ni₂MnGa ferromagnetic shape memory alloy was investigated. It is shown that Fe addition has little effect on the majority-spin density of state (DOS), but changes minority-spin DOS significantly. Substituting Fe for Mn decreases the total DOS of the parent phase, leading to the increase in parent phase stability. When Fe content is higher than 12.5at%, the increasing of martensitic transformation is related to the precipitation of γ phase.

A mathematical model of vibration power generation (VPG) with the giant magnetostrictive material (GMM) is proposed on the basis of the magneto-mechanical coupling model, Jiles-Atherton model and electromagnetic induction law. According to the model, the output voltage of a giant magnetostrictive power generator has been calculated under the condition of different vibration frequency, pre-stress and bias magnetic field. The calculating results show that the model can reveal the relationship between the input vibrating stress and output voltage. The experiment of a giant magnetostrictive power generator has been carried out, and the experimental results agree well with the calculating results.

Fe-Ga thin films were prepared by DC magnetron sputtering on Si (100) substrate and an alloy target consisting of Fe₈₁Ga₁₉ was used. X-ray diffraction techniques were used to quantify the strain in the Fe-Ga thin films by measuring the interplanar spacings of select crystallographic planes. The interplanar spacing, d, for the family of Fe-Ga {211} planes was measured. Using the well-established sin²ψ technique, the residual stress of the Fe-Ga thin films was calculated. It has been found that the stress for Fe-Ga thin films quickly increases with increasing the sputtering power. The residual stress of thin films is almost unchanged in the range of 220-440 nm, and then it decreases with increasing the thickness of thin films.

Epoxy shape memory polymers (SMPs) were preparation and their mechanical properties are focused on. Full shape recovery is observed at 150 °C for each polymer, and the SMP with lower hardener content shows a quicker shape recovery speed. In addition to a good thermal stability, glass transition temperature of the polymers increases with increasing hardener content. Of particular attention of DMA test is that the epoxy SMPs show a high storage modulus not only in glass state but also in rubber state. The tension test indicates that both stress at break and corresponding elastic modulus vary with a peak value for the polymers.

The present work aims to investigate the internal friction and effect of pre-deformation on damping capacity of Nb₆₀Ti₂₅Ni₁₅ alloy, which could be considered as TiNi/NbTi metal matrix composite. The internal friction results showed that this composite possesses excellent damping behavior, which is associated with the movement of a set of abundant interfaces, such as those between the TiNi and NbTi phases, those between martensitic variants and those between martensite and parent phase. Meanwhile, the peak temperature and the width of the internal peak increased with increasing of prestrain level. It appears to be due to the release of the stored elastic strain energy, or the pinning effect by the deformed structures. Furthermore, the height of internal friction peak decreased as the prestrain level increased.

This study presents part of an experimental and analytical survey of candidate methods for damage detection of composite structural. Embedded piezoceramic (PZT) sensors were excited with the high power ultrasonic wave generator generating a propagation of stress wave along the composite plate. The same embedded piezoceramic (PZT) sensors are used as receivers for acquiring stress signals. The effects of center frequency of embedded sensor were evaluated for the damage identification capability with known localized defects. The study was carried out to assess damage in composite plate by fusing information from multiple sensing paths of the embedded network. It was based on the Hilbert transform, signal correlation and probabilistic searching. The obtained results show that satisfactory detection of defects could be achieved by proposed method.

A miniature disk-pivot piezoelectric motor using a vibration mode B₁₁ of one nodal circle and one nodal diameter was investigated. Different from conventional wobble-type piezoelectric motor using piezoelectric rod or cylinder, a metal/piezoelectric disk is used to simulate the wobble vibration and an embedded metal cylinder is used to amplify the transverse displacement to obtain a much higher revolution speed over 10,000 rpm through the contact friction between the stator and rotor. The outer diameter of the metal/piezoelectric disk and the embedded cylinder is 14 mm and 2.5 mm, respectively. In order to avoid the coupling between the B₁₁ and any other vibration modes, the structure of the stator is analyzed using Finite Element Method (FEM) and optimized to avoid the influence between them. The simulations show that the stability of the disk-pivot piezoelectric motor will be influenced greatly when any other vibration mode is close to the mode B11. To separate the coupling modes, two structure parameters can be modified: the thickness of the piezoelectric ceramic and the height of the middle metal cylinder on the stator. And these methods were proved through testing some prototypes of the motors.

The pore characteristics and pore size distribution of porous near-equiatomic NiTi shape memory alloy fabricated by self-propagating high-temperature synthesis (SHS) are described in detail. The effects of different heat treatments on the transformation of porous NiTi alloy were investigated by differential scanning calorimetry (DSC), x-ray diffraction (XRD), and scanning electron microscopy (SEM). The results indicate that heat treatment had strong influences on the transformation temperatures and latent heats of transformation. When the porous alloy was annealed at 648K and 748K for 3.6ks, two steps transformation including R transformation occurred during cooling and heating and the R transformation temperatures are lower than B2↔B19' transformation temperatures. However, no transformation was detected within the experimental temperature range if the porous alloy was solution treated at 1133K for 2.4ks. This novel phenomenon was the results of extensive Ti2Ni intermetallic compound precipitation. The transformation temperatures of porous NiTi alloy after annealing at 1323K for 3.6ks were much lower than those of the untreated alloy.

This paper introduces a new based-on ultrasonic wave micro-fluid driving technique that is different from the present principle. The standing wave is generated by ultrasonic vibration in the device, and acoustic field is generated simultaneously. The particles in fluid medium of the device move towards the node of the standing waves caused by the effect of acoustic radiation pressure. A new device structure has been designed based on piezoelectric drive principle. The vibration modes and response has been obtained by FEA. The simulation results also indicate the feasibility of movements. Considering the influence of vibrator dimension, the dimension of the vibrator has been optimized. The experiment has been accomplished in the device with polystyrene spheres and achieves the enrichment of the particles.

Phase transformation, microstructure and mechanical property of Ni_50-x/2Ti_50-x/2Al_x (x=1, 2, 3 and 4 at.%) alloys have been investigated by electrical resistance (ER) measurement, scanning electron microscope (SEM), X ray diffraction (XRD) and tensile tests. The results show that a two-step phase transformation occurs from parent phase to R phase and subsequently to martensite upon cooling, and the transformation reverses upon heating. Both the martensitic transformation and R phase transformation temperatures decrease with increasing of Al content. The microstructure analysis indicates that the NiTi-Al alloys are composed of NiTi as the predominant phase and Ti₂Ni as the second phase mainly distributing at grain boundaries. The solid solution hardening effect of Al at room temperature has been demonstrated by the remarkable increasing of yielding strength and decreasing of tensile strain with increasing of Al content. Ni₄₉Ti₄₉Al₂ alloy deformed at the liquid temperature exhibits a maximum recoverable strain of 6.3%.

Fine pitch microprobe arrays are microneedle-like probes for inspecting the pixels of LCD panels or IC. They are usually made of multi-layers of metallic, nonmetallic, or combination of the two. The design requirement for a contacting force is less than 2 gf and a deflection should be less than 100 µm. Many microprobe shapes satisfying the design requirements are possible. A cantilever-type microprobe having many needles was chosen and optimized in this study. Several candidate shapes were chosen using topology and shape optimization technique subjected to design requirements. Then, the microprobe arrays were fabricated using the process applied for MEMS fabrication and they were made of BeNi, BeCu, or Si. The contact probing forces and deflections were measured for checking the results from optimum design by newly developed measuring equipment in our laboratory. Numerical and experimental results were compared and both showed a good correlation.

The torsion bar must be changed periodically due to its lack of durability and a phenomenon related to stress relaxation. Therefore technical development regarding the torsion bar's durability is urgently needed. In order to improve the fatigue life and durability of the dynamic components, new surface treatment technology such as ultrasonic shot peening, deep rolling, laser shock peening, etc. are developing widely. In this study, Ultrasonic Nanocrystal Surface Modification (UNSM) technology is applied as an advanced one to replace the presetting method (PM). UNSM and PM technology also induced the compressive residual stress on the surface layer of the torsion bar, which is the main improvement factor of fatigue life. DIN17221 material as a new MIL specification of torsion bar and SCM440 (as an alternative one to a old MIL-DTL-62567C) were processed with the UNSM technology to obtain the basic data and compare it between two, and then torsion fatigue tests of two materials were carried out to obtain the characteristics of torsion fatigue in this study.

It is advantageous to use a non-destructive evaluation (NDE) method to assess the mechanical properties of materials since conventional methods are time-consuming and usually require sampling from the material or component. In this study, an electrical resistivity method was attempted for the estimation of the creep damage of degraded 9Cr steel. The specimens with six different kinds of aging periods were prepared by an isothermal heat treatment at 690 °C. The electrical resistivity was determined by a standard DC four-point probe method at 24±0.5 °C. The home-made probe station and Burster 2304 were utilized for the resistance measurement. A correlation between the measured electrical resistivity and the tensile properties was studied. The electrical resistivity showed a declining tendency with the increase of aging time because the electrical resistivity is strongly dependent on the microstructural changes. A correlation between the electrical resistivity and aging parameter was established, which allows one to estimate the material degradation of 9Cr steel.

Sulfide stress corrosion cracking (SSCC) in crude oil field environment including hydrogen sulfide (H₂S) has been recognized as a materials failure mechanism. Welding residual stress generation and metallurgical change by fusion welding process increase the cracking driving force and reduce the resistance of brittle fracture as well as environmental fracture. On the base of this understanding, firstly, we analyzed welding residual stresses of welded ASTM A106 Gr B steel pipe using in the petrochemical plant. And next, SSCC tests were conducted to assess SSCC resistance of the weld with smooth specimens. From the result, influence of temperature on corrosion rate was sensitive in order of HAZ, base metal and weld metal. Therefore, the most sensitive region in the weld is HAZ, and its corrosion rate increases with the temperature of corrosion environment increase. And failure positions of the most cases among failed specimens were at HAZ of the weld. Low limit (σ_SSCC) of A106 Gr B steel pipe was assessed as 0.6 σ_y (7271.6N)

Mechanically polished surface of Zr₅₅Al₁₀Ni₅Cu₃₀ metallic glass was indented with a rigid ball 0.5 mm in diameter and its corresponding load-depth curve was recorded automatically. Although a stress-strain relationship beneath the indenter can be analyzed from the raw indentation curve, the current analysis developed for crystalline solids can mislead erroneous properties because it does not consider significant material pile-ups in amorphous metallic glasses. Thus, we proposed a novel indent image processing technique for characterizing the contact and flow properties in the metallic glasses; the contact area was measured by differentiating a three-dimensional indent morphology digitized by a surface profiler and a surface-stretching strain was newly defined in order to estimate the flow properties. Finally, the work-hardening index estimated was about 0.05, comparable with the typical value measured from uniaxial compression in the Zr-based metallic glass.

The concept of microfibrillar composite (MFC) has been used to create a new type of polymer composites, in which the reinforcing microfibrils are loaded with carbon nanotubes (CNT). Polyamide 66 (PA66) has been melt blended with polypropylene in a twin screw extruder with and without CNT, and thereafter cold drawn to create a fibrillar state as well as to align the CNT in the PA66 microfibrils. The drawn bristles were compression moulded at 180°C to prepare MFC plates. The scanning electron microscope (SEM) observations indicate near perfect distribution of CNT in the reinforcing PA66 microfibrils. Although the fibrillated PA66 is able to improve the tensile stiffness and strength as expected from the MFC structure, the incorporation of CNT does not exhibit any further enhancing effect. It rather adversely affects the mechanical properties due to poor interface adhesion between the matrix and the reinforcing microfibrils with the presence of CNT, as demonstrated by SEM. However, the resulting highly aligned CNT within the MFC are expected to affect the physical and functional properties of these composites.

Free-standing sub-micron Ti-5Al single crystal square pillars were fabricated along double slip and [0001] twinning orientations using FIB fabrication processes. Samples in range of 0.4 to 2.0µm were compressed. The yield stress increases much higher than their bulk counterpart as the specimen width decreases. The tendency of "smaller is stronger" is displayed in Ti-5Al single crystals loaded along and [0001] orientations. The number of slip systems is restricted by specimen physical size as it declines from 2µm to 0.5µm, when the specimens were subjected to double slip loading. Meanwhile, when sample size is less than 1.0µm, micro-pillars along twinning orientation have to compensate the incomplete twinning deformation via shearing due to geometrical restriction and dislocation starvation effects. This variation of deformation mode could be attributed to the starvation effect of dislocations.

Shikoku Electric Power Co., Inc. has developed the technology to manufacture a brand name "Finash" about 12 years ago, by sorting and classifying coal ash generated in coal fired power plants. "Finash" is highly functional fly ash (HFA) is produced by removing irregular coarse particles. It is important for the production of HFA to minimize the variation in quality of coal ash with sophisticated classification technique and extracting good-quality spherical fine particles. It is now widely utilized as concrete admixture for general civil engineering structures and buildings in Japan. When highly functional fly ash (HFA) is used as shotcrete admixture to substitute for fine aggregate of 100kg/m³, the shotcrete has the advantages of decreasing the amount of dust and rebound during spraying operation, improving the hardened properties of concrete, etc. Therefore, it has been applied in many tunnel construction projects. This paper discusses about the various characteristics such as construction placement, strength, neutralization and dry shrinkage of shotcrete using highly functional fly ash (HFA), using the results that is obtained from spray test in an actual road tunnel.

During the mid 1990s earthquakes in Northridge, California, and Kobe, Japan, illustrated a lack of understanding of the behaviour of structural steels exposed to seismic loads. Under this type of load regime, structural steel members are subjected to fully plastic load cycles and unexpectedly brittle failures may result.

A method for determining the accumulation of damage through cyclic pre-straining is proposed. Toughness, as defined by the area under the true stress strain curve, is used as an indicator of the level of damage that the steel has suffered and from this some idea of its remaining capacity to further deform can be determined.

Observations during the testing of these samples have indicated that there is a transition in the failure mode from a fatigue type failure, with a progressively growing crack, to an overload failure, in which the steel fails due to a lack of ability to further deform. Similar transitions have been noted by other researchers in the field. Analysis of the test results seems to show differences in the damage accumulation behaviour that may be used to identify when this transition in failure modes may occur.

Control over scale, dynamic, environment, and geometric errors in 5-axis machine tool are required to realize a high precision machine tool. Especially geometric errors such as translational, rotational, offset, and squareness errors are important factors which should be considered in the design stages of the machine tool. In this paper, geometric errors are evaluated for different configurations of 5-axis machine tool, namely, 1) table tilting, 2) head tilting, and 3) universal and their error synthesis models are derived. The proposed model is different from the conventional error synthesis model since it considers offset and offset errors. The volumetric error is estimated for every configuration with random geometric errors. Finally, the best configuration, the critical design parameter and error are suggested.

In this study, the relationship between the creep ductility and rupture life of 9Cr-1.5Mo steel with boron addition at 600°C was investigated by small punch (SP) creep test from the viewpoint of the modified Monkman-Grant relation. The amount of boron addition ranged from 0.0076wt% to 0.0196 wt%. The general concept of Monkman-Grant ductility for uniaxial creep was introduced and then particularly modified for the SP creep. The microstructure of the steel was observed to analyze the effect of boron addition on the creep ductility and rupture life. Based on the modified Monkman-Grant ductility for SP creep, it was found that the boron addition improved the creep ductility and rupture life of the 9Cr-1.5Mo steel. Also, the relationship between the minimum creep displacement rate and the amount of boron addition was analyzed.

The concrete mixer possesses the basic performance "mixing efficiency", and is one of the most important construction machines on the step that manufactures concrete. The bi-axial forced-mixing type of the mixer is high and the mixing efficiency is the highest. The flow patterns of this type mixer are divided into two: the locally crossing flow and the globally circulating flow. The globally circulating flow uniformly mixes fine particle materials that differ greatly the grain size turned on and are various and cement active. The locally crossing flow contributes to "Knead" to improve the contact frequency of the cement particle and water.

In the research, concrete was assumed to be a viscous model of one phase system for the model mixer of two types with different area of the locally crossing flow, the mixing efficiency curve of the model concrete of the high viscosity and the low viscosity was a process of becoming uniform with the axial rotation, and quantification was attempted. The second research tried the quantification of the crossing flow around the blade generated when two circulating flows crossed by the pressure fluctuation of the pressure sensor installed in the surface of the blade of the mixer was attempted, and the magnitude of the crossing Flow generated in the model mixer of two types and the correlation of the mixing efficiency curve were considered.

Titanium alloy has an attractive strength-to-weight ratio and good fatigue properties. However, the titanium alloy has very poor wear resistance, therefore, surface treatments must be considered in order to make the contact parts. Hard thin film deposited by PVD technique is well-known to improve the wear resistance. In this study, chromium nitride (CrN) film was applied to titanium alloy and its effect on the fatigue behavior was investigated. Ti-6Al-4V alloy was used as a substrate material. The CrN film was deposited by arc ion plating (AIP) method at two different negative bias voltages because the film hardness, crystal orientation and surface morphology were strongly depended on the bias voltage during the deposition. Tension-tension fatigue test and tensile test were carried out to investigate the fatigue properties. As the result, the fatigue strength was influenced by the deposition of the CrN film, especially, the fatigue strength was remarkable decreased by the deposition of the CrN film at high negative bias voltage compared to the uncoated specimen and the deposition of the CrN at low negative bias voltage. The difference of the fatigue strength was also investigated on the basis of crack initiating behavior during fatigue test and tensile test.

In order to study the fatigue damage formation process of ultrafine grained copper, fatigue tests were carried out for two samples: oxygen-free copper and deoxidized low-phosphorous copper. After the processing by equal channel angular pressing (ECAP) using eight passes, equiaxed grains with an average size of 300 nm were formed for both the samples. The formation behavior of surface damage was monitored. The effects of trace impurities on surface damage formation behavior were discussed from the viewpoints of change in surface morphological feature during stressing.

The corrosion resistance of aluminum can be improved by adding alloy elements or using a surface heat treatment process. The machine quality can be confirmed by analyzing the surface roughness, the surface hardness and the residual stress. In this paper, the fatigue characteristics of A6061-T6 aluminum specimens were obtained and compared with those of the treated specimens with the UNSM (Ultrasonic Nano-Crystal Surface Modification) technology and the untreated ones by using a multi-spindle rotating bending fatigue testing machine.

The fatigue crack initiation and fatigue lives of the treated specimens with the UNSM technology was delayed and extended by the UNSM effects that are the increase of surface hardness, and the reduction of the surface roughness.

Fatigue properties of Ti-6Al-4V (TC4) subjected to 0.9% physiological saline solutions were presented in this paper. The ultrasonic fatigue test method has been used to investigate the very high cycle fatigue properties of commercial titanium alloy TC4 with the microstructure of tramsformed lamellar dipped into 0.9% physiological saline solution prior to testing. Three estimated times have been decided for subjecting at 37 °C, such as 24 hours, 2 weeks and 4 weeks. The results show that physiological saline solution treatment makes a little influence on the ultrasonic fatigue life of TC4. The slope of S-N curve decreases as the dipping time increases. Dipping tests for three estimated times also have been performed. When TC4 has been dipped into physiological saline solution for 4 weeks, homogeneous white points have been observed on specular facet specimen. And in the fracture surface of which has been dipped for 4 weeks, new inclusion sized 5-10 µm in the crack initiation has been observed. The fractography pictures show the fracture to be transcrystalline plastic. Cracks are initiated because of the subsurface inclusion and the facet slip of α-phase.

In this paper the frictional heating effect on the propagation of surface crack under Hertzian contact loading based on the fracture mechanics is investigated. For the theoretical analysis of this effect, we estimated stress intensity factor of surface crack -tip in shear mode under Hertzian contact sliding friction. Theoretical results showed those thermal loads (Th), Peclet number (Pe) and crack angle (β) are very important factors on the propagation of surface crack under Hertzian contact loading. When thermal load(Th) and Peclet number(Pe) are constant, maximum variable range of stress intensity factor, ΔKII, is located in the range of surface crack angle 130°~150°. Non-dimensional parameter T consisting of thermal load and peclet number for evaluating ceramic wear behavior is introduced.

Since the thin film technology is applied to micro-machines, MEMS (micro electro-mechanical system), optical devices and others, the evaluation of mechanical properties in thin films becomes to be important. On the other hand, there are differences in mechanical properties between bulk materials and thin films, but studies in this field have not yet been made enough. The present paper reports on the evaluation of the mechanical properties of Cu thin films with and without AlN passivation layer. Specimens with different thickness of Cu film were subjected to cyclic plane bending fatigue test. Residual stresses developed in the Cu films were measured in a sequence of bending cycles using X-ray diffraction method in order to understand the effect of film thickness and passivation layer on mechanical properties of Cu thin films.

A fully dense electrodeposited microcrystalline copper with nano-scale twins was synthesized by electrodeposition. The microstructure of this copper was analyzed X-ray diffractometer (XRD) and by transmission electron microscopy (TEM). The grains of mean size about 2mm were divided by high density of growth twins with mean lamellar thickness of about 90 nm. Tensile tests at different strain rates and room temperature showed that the strength increased from 379 MPa to 458 MPa with strain rate increasing from 10^-5 s^-1 to 0.1 s^-1. The elongations to fracture were in the range of 13.6~15.5%. So this Cu has good combination of strength and ductility. The strengths are much higher than that determined by Hall-Petch relation with the same grain size, which means that twin boundaries are effective in blocking dislocation motion. The strain rate sensitivity and activation volume estimated from the flow stress versus strain curves was 0.016 and 84 b³~69b³, respectively. Such a large activation volume indicates that the deformation of this copper was controlled by dislocation process.

In this study, not only bending strength of Super-lightweight mortar (SLM) but also resistance to impact load of it, with several types of PVA fibers of different lengths and diameters, were investigated. It was shown that, when the diameter of the fiber decreased and fiber-volume fraction increased, bending strength and resistance to the impact load were generally improved. However, the effect of the performance improvement of the SLM showed the tendency to become small in mix proportion that has too large total surface area of fiber.

An experimental investigation was carried out to evaluate the fracture pressure and behaviors of ceramic materials for a dome port cover of an air breathing engine. The experiments were performed in a shock tube, which had a working section of 70 mm in diameter and a total length of 6 m in the shock tube. The response pressure transducers were used to measure expansion pressure and reflection pressure of working section near the end edge of the shock tube. Fractured specimens collected from the dump tank were investigated for the fracture phenomenon of ceramics after testing. The fracture pressure increases as a specimen thickness increases, and as the specimen diameter decreases, respectively. The driven gas pressures P₂ obtained from theory and experiment agree well. The reflection wave pressures P₅ agree well comparatively with both results of equation and experiment at low pressure of P₄, but they do not agree well at high pressure of P₄. The fracture phenomena of the plate and dome specimens at the same diameter are broken into small particles in various thicknesses, but the fracture phenomenon of the plate specimen is not broken into the particles as specimen diameter decreases.

During an injection molding of composite materials, fiber attrition occurs and the average fiber length is reduced. In order to control the breakage of fibers and degradation of mechanical properties during processing, Flat glass Fiber (FF), that has oval cross-section shape, has been developed to use for glass fiber reinforced thermoplastic (GFRTP). Using FF as reinforcement of GFRTP has advantages as following: (1) Fluidity of FF is better than conventional Normal glass Fiber (NF) with 'circular' cross-section; (2) Fiber breakage during the injection molding process using FF is smaller than that using NF. In this study, the mechanical properties of FF and NF were compared for reinforcement of long fiber thermoplastics pellets (LFT pellets). We have also investigated the effect of screw design on fiber damage and the mechanical properties. The mechanical properties of specimens molded by FF reinforcement LFT (FF-LFT) pellets were superior to these of NF reinforcement LFT (NF-LFT) pellets. The former could give composites with higher fluidity and longer residual fiber length. Moreover, FF was able to strengthen injection-molded samples with higher fiber content than NF. Low shear type screw was effective to prevent the fiber attrition during plasticization process, hence leads to better mechanical properties of GFRTP

Incoloy 800, which is used within steam generator tubes, is a heat resistant material since it is an iron-nickel-chromium alloy. However, construction of a systematic database is needed to receive integrity data defecting insurance of specific data about room and elevated temperature fretting fatigue behavior for Incoloy 800. Accordingly, this study investigates the specific change in fatigue limitations under the condition of the fretting fatigue as compared to that under the condition of the plain fatigue by performing plain and fretting fatigue tests on Incoloy 800 at 320°C, real operating temperature and at room-temperature, respectively. The change in the frictional force is measured during the fretting fatigue testing against the repeated cycle, and the mechanism of fretting fatigue is investigated through the observation of the fatigue-fracture surface.

This paper deals with a device and method for measuring the impact properties of artificial turf surface using the accelerometer. Recently, the number of artificial turf ground is increasing according to holding a variety of international games and change of school play ground to artificial turf from clay. Artificial turf ground is required to meet standard certification to play international game. This standard certification is given by shock performance test during the specified period. The automatic shock evaluation system for shock absorbing performance test of artificial turf ground is proposed. This system consisted of auto carriage moving module, auto shock performance testing module, and auto data acquisition. Experiment is conducted to verify the performance of developed automatic shock evaluation system for shock absorbing performance test of artificial turf ground. From the performance test, developed automatic shock evaluation system has drop height of 55mm with resolution of 0.5mm, resolution of ±1% for operating range, measuring acceleration of over 50g, sampling frequency of over 10kHz, image resolution of over 12bit.

An experimental study on material characterization of SMC (Sheet Molding Compounds) compression molded parts was carried out by 3-point bending tests and creep tests. And computer simulation of optimum condition of SMC design was carried out by finite element analysis. The thicknesses of SMC specimen were 6.5, 7, 7.5 and 8mm and the angles of inclination were 0°, 2.5°, 5°, 7.5° and 10°. After static load test, the stress of SMC was different at the each condition. The influence of angles of inclination was important. The maximum stress occurred at 0°. But the more angle of inclination was big, the more maximum stress was small. The decrement was big at the range of 0° to 2.5°. The influence of thicknesses also was important. The more thickness was large, the more maximum stress was small.

This paper examined the biomechanical fatigue behavior of Achilles tendon autograft after posterior cruciate ligament (PLC) reconstructions. It experimented with various fixation devices and locations on the degree of initial lengthening and slippage to investigate the relationship between lengthening and slippage ratios among calcaneal and soft tissue fixation methods. Eight specimens of proximal tibia and Achilles tendon grafts were harvested from cadavers and classified into four groups according to the type of transtibial fixation technique. A cyclic load ranging from 50N to 250N was applied to each graft when fixed to the proximal tibia at 55 degrees. The soft tissue fixation method, which uses an interference screw, demonstrated a 56.4% ratio of slippage to total elongation. The use of a double cross-pin with the same method demonstrated a 45.4% slippage ratio. The former was associated with approximately 2 mm less total elongation and 13% more slippage than lengthening compared to the latter. This result was predominantly due to the poor standard of fixation compared to the same method using a double cross-pin.

A 304 stainless steel short fiber reinforced aluminum composite was fabricated and investigated for matrix voids as well as interfacial reaction using ultrasound. The aluminum composite was made by a hot isostatic pressing technique at a temperature of 600°C and subsequent aging at 120°C. The tensile strength significantly increased with the addition of 5% stainless steel fiber. The interfacial reaction evolved and grew with aging time due to generation of intermetallic FeAl₂. The ultrasonic nonlinearity (β/β₀) increased with the volume fraction of fiber and aging heat treatment because of the generation of microvoids resulted from localized fibers and matrix precipitation. This study demonstrates the potential for characterization of reinforced composite materials fabricated by the powder metallurgy technique.

The tensile responses and the associated damage evolutions of a 3D C/SiC composite with and without heat treatment on the fiber preforms were compared. The results show that the composite without heat treatment exhibits a largely non-linear stress-strain behavior up to rupture as well as a lower strength and a strain-to-failure. The damage evolution characterized by acoustic emission indicates the composite failures in the region of matrix cracking multiplication. However, the composite with heat treatment has a larger strength and a strain-to-failure, and the damage evolution indicates that the composite had experienced the region of matrix cracking saturation and then fiber bundle pull-out just prior to final failure. Microstructural observations on the fractured specimens revealed the interfacial bonding between fibers and matrix becomes weaker after heat treatment.

The degradation behaviors of EPDM (ethylene-propylene diene monomer) rubbers used for automotive radiator hoses subjected to thermo-oxidative and electrochemical stresses were studied. As a result of the thermo-oxidative aging tests, the IRHD (international rubber hardness degrees) hardness of the rubber specimens increased, while their elongation at break decreased much. A slight increase in crosslink density indicated that changes in the properties were caused by the concentration of carbonyl groups in the skin layer. For the electrochemical degradation (ECD), the weight of rubber specimens increased whereas their elongation and hardness much decreased because water solution penetrated into the skin part. There was little change in crosslink density. Formation of many chain scissions and thus microvoid networks in the skin layer induced the swelling behavior leading to a linear reduction of hardness versus the weight increase.

In nuclear power plant, fretting wear due to a combination of impact and sliding motions of the U-tubes against the supports and/or foreign objects caused by flow induced vibration, can make a serious problem in steam generator. A test rig, fretting wear simulator, is developed to elucidate fretting wear mechanism qualitatively and quantitatively. The realistic condition of steam generator of high temperature up to 320°C, high pressure up to 15 MPa, and water environment could be achieved by a test rig. The fretting wear simulator consists of main frame, water loop system, and control unit. Actual contact region under a realistic condition of steam generator was isolated using autoclave. Effects of various parameters such as the amounts of impact and sliding motions, applied loads and initial gaps and so forth are considered in this research. After the experiment, wear damage was measured by a three-dimensional profiler and the surface was also studied by SEM microscopically. Initial results were also presented.

In this paper, the dynamic stability of a rotating cantilever pipe conveying fluid with a crack and tip mass is investigated by numerical method. That is, the effects of the rotating the rotating angular velocity, the mass ratio, the crack and tip mass on the critical flow velocity for flutter instability of system are studied. The equations of motion of rotating pipe are derived by using the extended Hamilton's principle. The crack section of pipe is represented by a local flexibility matrix connecting two undamaged pipe segments. The crack is assumed to be in the first mode of fracture and always opened during the vibrations. Finally, the stability maps of the cracked rotating pipe system as a rotating angular velocity and mass ratio β are presented.

The fatigue crack propagation of CFRP (carbon fiber reinforced composite material) laminates is of current interest, particularly with regard to their durability under fatigue loading. Recently, carbon fiber reinforced composite materials (Woven fabric) are widely used in various fields of engineering because of its advanced properties. Then, many researchers have studied woven fabric CFRP materials but fatigue crack propagation behaviors for composites have not been still standardized . It shows the different crack propagation behavior according to load and fiber direction. Therefore, there is a need to consider fatigue crack propagation behavior in conformity with fiber arraying direction to load direction at designing structure using woven CFRP materials. In this study, therefore, the fatigue crack propagation for plain woven CFRP composite materials was investigated under two different fiber array direction (fiber arraying direction to load : 0°, 45°). Fatigue crack propagation tests of the woven CFRP composite were conducted under sinusoidal wave-form with stress ratios of 0.3 at a frequency of 10Hz, respectively. As a result of test, fatigue crack propagation rates (da/dN) were plotted against the stress-intensity factor amplitude (ΔK) and other factor. Also we compared ΔK with other factor that considering in-plain anisotropy. All of tests of fatigue crack propagation were carried out under mode I opening loading by using compact tension specimens.

The purpose of this study is to investigate experimentally the hardness distributions and micro-structural properties of the dissimilar joints using chrome molybdenum steel (SCM440) to carbon steel (S45C) parts. The experiments were carried out using a beforehand designed and constructed experimental friction welding set-up, constructed as a continuous-drive brake type. The pilot dissimilar welding experiments under different friction pressure and friction time were carried out to obtain optimum welding parameters using visual examination and tensile tests. Vicker's hardness distributions and microstructures in the interfaces of the dissimilar joints for PWHT were also obtained and examined. The obtained results were compared with those of the previous study.

The basic concept and preliminary performance results of a miniaturized electroosmotic pump with diaphragms were included in the present study. The separation of an electroosmotic pumping liquid from a drug using diaphragms is mainly to have a freedom in choosing an electroosmotic pumping liquid and to achieve the optimal drug delivery with its preferable precise control. As a result, the maximum flow rate and current increased linearly according to the increment of applied voltage that is electric potential.

Dynamic mechanical behaviors of Mg-Gd-Y series extruded magnesium alloy and its σ-εcurves are measured by using of Hopkinson pressure bar technique. According to the concept of efficiency of absorption energy, this thesis compares Mg-Gd-Y series extruded alloy with ZK60 extruded magnesium alloy. Being obtained similitude numbers by means of normalizing processing for governing equations of the continuum mechanics and according to the viewpoint of equal density of area, the comparative experiment of anti-projectile capabilities is elaborately designed between Mg-Gd-Y alloy and the 7A52 aluminum alloy. The result has validated that anti-projectile capability of Mg-Gd-Y alloy is better than those of 7A52 alloy under the condition of equal density of area. The relative technique approaches for improving anti-projectile capability of Mg-Gd-Y alloy are put forward making use of similitude numbers. Finally, the basic characters of effect of adiabatic shear are revealed by micro analysis.

In this study, the mass fabrication of microelectrode tools for microelectrochemical machining (MECM) was studied using microfabrication processes. The cantilever type geometry of microelectrodes was defined by photolithography processes, and metal patterns were made for electrical contacts. Various fabrication processes were studied for the fabrication of microelectrode tools, such as wet etching, lift-off, and electroforming for metal layer patterning. MECM test results showed feasibility of the fabricated electrode tools. The microfabricated electrodes can be used as micromachining tools for various electrical micromachining of steel mold and parts of microdevices.

At first, the specimens of SKD-61 are prepared and tested to verify the effects of ultrasonic nano-crystal surface modification (UNSM) technology on the variation of mechanical properties under static load variation. 20 kHz frequency was applied to the ball tip, and the applied static forces were changed three kinds of load level 40, 60, and 80 N, respectively. The grain size of SKD-61 surface treated by UNSM becomes very fine to nano-scale crystal and structure is observed till certain depth. The compressive residual stress becomes -810, -1200 and -1400 MPa to a 150 µm depth after the UNSM process according to three kinds of load level 40, 60, and 80 N, respectively. Fatigue limits of 10⁷ cycles are increased by 8.3, 11.2, and 17.9% after UNSM at the smooth specimen according to three kinds of load level, respectively. Interior-originating fracture, fish-eye crack, occurs after UNSM because of a nano structured modification by a surface plastic deformation and compressive residual stress in the case of the smooth specimen. UNSM improves the mechanical properties effectively and is becoming a practical method to improve the service life of the trimming knives. Productivity and reliability of a cold rolling process have improved more than 2 times by the application of the UNSM trimming knives.

An optical method has been applied to measure the elastic modulus of a beetle wing membrane. A specimen was prepared by cutting the beetle wing carefully to take a sample size of 5.0 mm in width and 7.5 mm in length. We used a scanning electron microscope for the exact measurement of the membrane thickness of a beetle wing. It was attached to a fixture in order to induce a uniform displacement using a micromanipulator. We measured the applied load by the use of a load cell with a maximum capacity of 5 N and the corresponding displacement was measured by means of an ARAMIS system based on the digital image correlation method. The measured thickness of the beetle wing varied from point to point of the wing part and the elastic modulus was different according to the loading direction. In conclusion, we successfully measured the elastic modulus of a beetle wing with an ARAMIS system based on an optics based measurement method.

This paper aims to evaluate the effect of temperature on impact damage resistance of glass/epoxy laminates. A series of impact tests were performed using an instrumented impact-testing machine at temperature ranging from -40°C to +80°C. The resulting impact damage was measured using back light method. The impact resistance parameters were employed to understand the damage resistance. It was observed that temperature has a little effect on the impact responses of composite laminates. The damage resistance of glass/epoxy laminates is somewhat deteriorated at two opposite extremes of the studied temperature range and this behavior is likely due to the property change of glass/epoxy laminates under extreme temperatures

The superconductors Bi₂Sr₂CaCu₂O_x (Bi2212 ) and Ag/Bi2212 composites samples were prepared by the powder metallurgy method. The frictional behaviors of Bi2212 pins in contact with stainless steel plate were examined from -196 to 20°C on friction and wear tester. When the temperature was lower than the superconducting transition temperature, the friction coefficient of Bi2212 dropped sharply, and it kept 0.11 with increase of the test time. The microstructure and morphology of Ag/Bi2212 composites were investigated by means of X-ray diffraction (XRD), transmission electronic microscope (TEM) and high resolution transmission electronic microscope (HRTEM). The elemental compositions of the worn surfaces of Ag/Bi2212 composites were determined by using energy dispersive X-ray analysis (EDXA). The results showed that the superconducting structure of Bi2212 was not changed and Ag was distributed in the Bi2212 matrix. Ag doping improved the toughness of oxide ceramics Bi2212. The friction test results of Ag/Bi2212 composites showed the tribological properties were improved at room temperature. The friction coefficient of 10%Ag/Bi2212 against stainless steel showed a lower value (0.2) and the wear rate of 15%Ag/Bi2212 was minimum (9.5×10^-5 mm³·(N·m)^-1 ). The lubrication of soft metallic film and load of hard matrix were the mechanism of decreased friction and anti-wear of Ag/Bi2212 composites.

The fractional quantitative computed tomography (fQCT) to determine both quantity and distribution of bone mineral was evaluated based on the mechanical properties of trabecular bone. Using quantitative computed tomography (QCT), bone mineral density was measured at 46 areas from 5 bovine tibias. Subsequently, fQCT was measured by the proportion of pixels showing a bone mineral density greater than 290 mg/ml. Based on the mechanical properties of the bone specimens, the QCT and the fQCT were compared. The fQCT showed a significant correlation with the compressive strength with superiority to the QCT.

The heavy duty diesel engine must have a large output for maintaining excellent mobility. In this study, a three-dimensional finite element model of a heavy-duty diesel engine was developed to conduct the stress analysis by using property of CGI. The compacted graphite iron (CGI) is a material currently under study for the engine demanded for high torque, durability, stiffness, and fatigue. The FE model of the heavy duty diesel engine section consisting of four half cylinders was selected. The heavy duty diesel engine section includes a cylinder block, a cylinder head, a gasket, a liner, a bearing cap, bearing and bolts. The loading conditions of engine are pre-fit load, assembly load, and gas load. A structural analysis on the result was performed in order to optimize on the cylinder block of the diesel engine.

This paper has reported the effect of oxygen and argon plasma treatments of CIIR rubber using Attenuated Total Reflectance (ATR) and surface energy measurements. Plasma treatment led to changes in the surface energy from 31 to 45.7 mN/m. Plasma treatment conditions influenced both the changes in surface energy and stability, and they also became more difficult to obtain good contact angle measurements. However, plasma treatments made the interfacial properties to be stabilized. ATR measurements revealed that changes in surface energy with treatment time are due mostly to increased oxygen functionality.

The adhesion force between a chloride-isobutene-isoprene rubber (CIIR) and stainless steel ball was studied. To decrease the adhesion force, the CIIR rubber was treated with high-density microwave plasma employing oxygen and argon gases. The experimental results showed that the adhesion force decreases with increasing the time of oxygen and argon plasma treatments. In addition, the contact microscope measurements revealed different surface structure with two gases. The real contact area also decreased with treatment time and dramatic changes were observed after 5 min treatment of CIIR rubber. The field emission scanning electron microscope image also showed that the subsurface of CIIR rubber pattern has changed with various plasma treatments. These results imply change in the morphology of CIIR rubber surface by plasma treatment is one reason for the decrease in adhesion forces.

The microstructures and mechanical properties of Ni_50-xTi_43+xAl₆Mo₁ (x= 0.5, 1, 1.5, 3.5, 5.5 and 7 at. %) alloys have been investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) and compressive tests. We found that the variation of Ni/Ti ratio is the predominant reason for affecting the yield stress. The yield stress at room temperature of Ni-rich and Ti-rich alloys was higher than that of the equi-atomic alloy due to the strong solid solution hardening caused by the variation of Ni/Ti ratio. The size and volume fraction of Ti₂Ni phase decreased with increasing Ni/Ti ratio. The yield stress at 600°C and 700°C increased with the increasing volume fraction of Ti₂Ni phase due to the precipitation hardening effect. The precipitation hardening effect was weakened with increasing temperature. For the Ti-rich alloy deformed at 800°C, the yield stress deceased with the increasing of Ni/Ti ratio due to the reduced strength and unfavorable distribution of Ti₂Ni.

The friction and wear of silicon nitride (Si₃N₄) against silicon nitride (Si₃N₄) and zirconia (Y–TZP) and chilled cast iron and Alumina sliding under dry friction at room temperature conditions were investigated with pin-on-disk tribometer at sliding speed of 0.56ms^-1 and normal load of 50N, 80N, respectively. Based on the variety regulation of the wear maps, the wear mechanisms of the two couples were analyzed. Get the result of friction coefficient and maps of wear Rate of the Pin and the Disk. The results of comparing this couple is Si₃N₄/ chilled cast iron < Si₃N₄/ ZrO₂< Si₃N₄/ Si₃N₄< Si₃N₄/ Al₂O₃.

Different pretreatment methods for electroless nickel and cobalt plating are demonstrated and compared in the present investigation. The surface morphologies of the nickel or cobalt deposits are investigated by scanning electron microscopy (SEM), and the chemical compositions of the coatings are analyzed by energy-dispersive X-ray spectroscopy (EDX). Method of single-step pretreatment is selected as the optimized method for electroless nickel plating process, while improved two-step sensitization-activation and single-step pretreatment methods can be selected for electroless cobalt plating. It can be found that the content of free Co is much lower compared to electroless Ni plating.

An experimental study was conducted to examine the effect of cyclic hygrothermal environment on the interfacial property of CCF300/BMI composites. The moisture weight and interlaminar shear strength of CCF300/BMI composites specimen of each stage during three absorption-desorption cyclical stages was investigated. The results showed the ILSS of composites after water absorption dramatically decreased, but it could make a comeback on the whole after removal of water.

In this paper, a new adaptive finite element (FE) framework based on the variational multiscale method is proposed and applied to simulate the dynamic behaviors of metal under loadings. First, the extended bridging scale method is used to couple molecular dynamics and FE. Then, macro damages evolvements of those micro defects are simulated by the adaptive FE method. Some auxiliary strategies, such as the conservative mesh remapping, failure mechanism and mesh splitting technique are also included in the adaptive FE computation. Efficiency of our method is validated by numerical experiments.

The driver airbag system is designed as a supplemental restraint system in addition to the seatbelt, and is designed to protect the driver's head and chest against severe injury by a device that is actuated in case of vehicle's fronted impact. Deployment of an airbag module with floating horn assembly is a highly dynamic process. The concept of driver airbag module with floating horn assembly and aluminum emblem is presented as a useful parameter when the airbag deploys and the energy is evaluated as performance factor in airbag module. Floating horn assembly is also one of the major factors for driver airbag module design to perform its horn function and check the package between driver airbag module and steering wheel.

This study on the design of driver airbag module with floating horn assembly proved the feasibility as a new safety device. However, the system level study is needed for decrease of passenger injury. This study can be used for the implementation of a prototype of DABM with floating horn device.

Modern optimization techniques, such as the steepest descent method, Newton's method, Rosen's gradient projection method, genetic algorithms, etc., have been developed and quickly improved with the progress of digital computers. The steepest descent method and Newton's method are applied efficiently to unconstrained problems. For many engineering problems involving constraints, the genetic algorithm and SUMT¹are applied with relative ease.

Genetic algorithms²have global search characteristics and relatively good convergence rates. Recently, a Successive Zooming Genetic Algorithm (SZGA)^3,4 was introduced that can search the precise optimal solution at any level of desired accuracy. In the case of engineering problems involving an equality constraint, even if good optimization techniques are applied to the constraint problems, a proper constraint range can lead to a more rapid convergence and precise solution.

This study investigated the proper band-width of an equality constraint using the Successive Zooming Genetic Algorithm (SZGA) technique both theoretically and numerically. We were able to find a certain band-width range of the rapid convergence for each problem, and a broad but more general one too.

Improving position accuracy of multi-axis machine tools is widely researched. The best known and widely used parametric approach models the direct kinematics of the work-piece and tool kinematic chain and use error synthesis modeling composed of homogeneous transform matrix (HTM). With respect to five axis machine tools, the increase in the number of axis and consideration of different configuration make computation of error matrices difficult and result in long error equations. In addition it becomes difficult to interpret the physical meaning of error terms in these equations. This work presents a mathematical formulation of error synthesis modeling for multi-axis system with the general joint series. This formula can be applied to all possible configurations.

The geometric model for an arbitrary joint is defined which is applicable to either prismatic or rotary joint. The error synthesis model for any configuration can be computed from the kinematic chains of a series of arbitrary joints. The proposed model consists of combination of error components of each local axis. Hence it is intuitive and easy to understand the effect of origin offset of local coordinates and squareness error with reference to the measurement coordinate.

We study systematically the site occupancy and effects of alloying element on NiAl bonds character of 4d transition metals by first-principles method based on density functional theory. The impurity formation energies of 4d TM of NiAl in Al-site and Ni-site are calculated. Y, Zr, Nb, Cd prefer to occupy the Al-site, whereas Mo, Tc, Ru, Rh, Pd, Ag prefers to occupy Ni-site. Crystal distortion and the overlap population between the alloying element and its first-neighboring atoms and are also calculated. The result shows that the substituting Al-site the elements Y, Zr, Nb, Cd interact with its first-neighboring Ni atom by anti-bonding. The total covalent ratio is decreased by theses elements which may improve ductility of NiAl. For Ni-site elements, the interaction between the alloying element Mo (Tc, Ru, Rh, Pd, and Ag) with its first-neighboring atoms Al also shows decrease in covalent. Site occupation of 4d transition metals are also discussed by the reaction energy for formation Ni₂TiX and X bulk phase.

We employed a first-principles method based on the density functional theory to investigate the effect of impurity O on the site preference and elastic properties of α₂-Ti₃Al. We found that the O atom prefers to occupy the Ti-rich octahedral interstitial site in α₂-Ti₃Al. We calculated the elastic constants of α₂-Ti₃Al with single O atom, which demonstrate that the O presence has no large effect on α₂-Ti₃Al according to the empirical criterions. Other factors such as O cluster should be taken into account to understand the deleterious effect of O on α₂-Ti₃Al. Our results provide a useful reference to further study the mechanical properties of TiAl alloys.

The cohesive energies of Ag nanoclusters E_c(N) in truncated octahedron (TO), icosahedron (IH) and truncated decahedron (DH) structures are evaluated through both theory and Density Function theory (DFT) simulation where N denotes the atom number. In the theoretical calculation, through relating E_c(N) values to the total bond numbers of clusters, E_c(N) value of IH structure is found to be the lowest at any N. In DFT simulation, E_c(N) values are separately evaluated before and after geometry optimization. IH structure is always favorable to exist when clusters are un-relaxed, agreed with the theoretical calculation. When the clusters are relaxed, the structural stability becomes selective and low-symmetric TO and DH structures are respectively stable at some specific size. The reason of the difference on E_c(N) values between two methods is compared. Both methods indicate that E_c(N) values of the clusters are larger than those of the corresponding bulk crystals E_cb.

The non-isothermal polycrystalline solidification of a binary alloy is simulated by employing a phase field model which takes into account the heat transition and the random crystallographic orientation. The stochastic nucleation is taken into account in the simulation through the Poisson seeding algorithm and a kinetic calculation for binary melts based on the classical nucleation theory. Different microstructures are obtained under various cooling conditions. It is found that the grain structure becomes finer with increasing the cooling rate, which agrees with experimental result.

The establishment of solute boundary layer is studied by using a quantitative phase field model during the initial transient stage of binary alloys solidification. Results reveal that the time-dependent solute distribution shows good agreements with the previous analytical results. The planar instability is discussed according to the time-dependent constitutional supercooling with different pulling velocities. Moreover, the critical pulling velocity of planar instability can be obtained by investigating the interface velocity of the critical instability with different pulling velocities.

A novel model for predicting the fatigue crack growth had been developed based on the concept of the fatigue damage accumulation. Fatigue crack growth was considered as a process of continuous crack nucleation. The crack tip failed to form a fresh crack while the accumulative fatigue damage reached the critical damage. A simplified model of the general crack growth model was proposed with the assumption that the damage zone can be divided into many different zones and each zone had the same crack growth rate. The model was applied to predict the crack growth of the compact specimen made of 16MnR steel under the constant amplitude loading. The predicted crack growth rate was in excellent agreement with the experimental observations.

In the present study, we measured velocity vector fields around hoop rings at each divided sections by using a particle image velocimetry method. The ring model used in this study was made of brass with two different aspect ratios and the experiment is carried out in a circulating water channel. As a result, we can observe two counter-rotating vortical flow structures around each hoop regime that is attributed to the interaction between direct pass through flow of hoop center and the shear flow separated from sharp-edged end of ring hoop.

Whirling is a cutting process in which a series of cutting edges remove material by turning over the rotating workpiece. In this process, the whirling ring with a number of cutting teeth combined with the rotation and advancement of workpiece, produces pitches of worm. Mechanics of chip formation of the process, however, has not been fully estabilished. To estimate the cutting force during the process, the kinematics and the maximum undeformed chip thickness to be removed by each cutting edge should be thoroughly analyzed.

In this study, using the recently developed model of undeformed chip thickness and the DEFORM software, cutting forces of the whirling process are estimated. The effects of cutting forces on tool are analyzed using the ADAMS software. The validity of the simulations has been verified with a series of cutting experiments.

In metal cutting practices, for a given tool material, tool geometry is a very important element and must be carefully designed in relation to the workpiece material to be machined. Patterns of tool stress are varying with input cutting conditions; however, effects of tool geometry on tool stress are not clearly understood. The load distribution on tool face is affected by the tool geometry and this causes the change of the stress distribution on the tool.

Reactor coolant loop (RCL) pipes circulating the heat generated in a nuclear power plant consist of so large diameter pipes that the installation of these pipes is one of the major construction processes. Conventionally, a shield metal arc welding (SMAW) process has been mainly used in RCL piping installations, which sometimes caused severe deformations, dislocation of main equipments and various other complications due to excessive heat input in welding processes. Hence, automation of the work of welding is required and narrow-gap welding (NGW) process is being reviewed for new nuclear power plants as an alternative method of welding. In this study, transient heat transfer and thermo-elastic-plastic analyses have been performed for the residual stress distribution on the narrow gap weldment of RCL by finite element method under various conditions including surface heat flux and temperature dependent thermo-physical properties.

Even though several finite element models of lumbar spine were introduced, there has been no model including the neural structure. Therefore, the authors made the novel lumbar spine finite element model including neural structure. Using this model, we investigated the relation between the deformity pattern and nerve root stress. Two lumbar models with different types of curve pattern (lateral bending and lateral bending with rotation curve) were made. In the model of lateral bending curves without rotation, the principal compressive nerve root stress on the concave side was greater than the principal tensile stress on the convex side at the apex vertebra. Contrarily, in the lateral bending curve with rotational deformity, the nerve stress on the convex side was higher than that on the concave side. Therefore, this study elicit that deformity pattern could have significantly influence on the nerve root stress in the lumbar spine.

To examine earthquake response characteristics of hysteresis damper using SLY120 and SS400 steel panel damper, earthquake response test were performed. In this paper, restoring force characteristic of hysteresis damper which is obtained by loading test are assessed using numerical analysis model. A skeleton shift model, which has been used frequently in conventional analysis, is applied. Using a hybrid earthquake response test system, various characteristics of structural components that are difficult to model and to express mathematically are detected by test and incorporated into the computer system to promote numerical analysis of the whole system. In this research, hybrid earthquake response simulation of the linked vibration suppression structure is carried out, whereas hysteresis damper at the linked vibration control structure are selected as the actual loading test part and the peripheral frame is considered to be the virtual structure part.

This paper is associated with the manufacture of 60W Transverse Flux Linear Motor (TFLM), and the thrust force and the maximum displacement of TFLM is compared with Longitudinal Flux Linear Motor (LFLM). Thus, the force which follows in location of the electric motor is simulated with ANSYS, and the thrust force of the linear actuator with applied current is tested. And the experiment results by several cases of alternating current is reported.

Permanent Magnet (PM) type Longitudinal Flux Linear Motors (LFLMs) are electromagnetic devices which can develop directly powerful linear motion. This paper presents statistical optimum design of PM type LFLM to reduce the weight of the machine with the constraints of avg. thrust force using the penalty method with characteristics function and Response Surface Methodology (RSM). The contribution and effect of the each design variable on the characteristic function is evaluated by the analysis of means (ANOM) and optimum design set is determined. The reduced gradient algorithm is adopted in RSM. Therefore, it is expected that the proposed optimization procedure using penalty method and RSM can be easily utilized to solve the optimization problem with constraint of electric machine.

Zinc oxide has received extensive attention for its unique luminescence properties. In this paper, ZnO granular films were prepared on the Si wafer and quartz substrate by Layer-by-Layer electrostatic self-assembly method. The effect of sol concentration on particle size and photoluminescence properties was investigated. SEM images indicate that ZnO particle size increases with sol concentration improving. Absorption edge and photoluminescence peak have a red-shift with particle size increase. The emission peak shift is resulted from particle size effect and the change of oxygen vacancy concentration in surface. The luminescent property of granular film shows big difference with that of ZnO sol. This difference is related to the assembly state of ZnO nanoparticles.

Plating thin Palladium (Pd) film on the outer surface of a porous stainless steel tube enables very rapid hydrogen permeation with an absolute selectivity. Methane steam reforming for hydrogen production is performed in a Pd membrane reactor. In this reaction, carbon monoxide (CO) synthesized is known to affect hydrogen permeability. The effect on hydrogen permeability and the membrane stability were investigated. After hydrogen was flowed through Pd membrane for 1 hour, CO (1%, 10%, 100% diluted by helium) was flowed on the membrane for 1 hour, and hydrogen was re-permeated through the membrane. Under the all experiment, the temperature, the differential pressure and the flow rate of non-permeation side were 823K, 0.1 MPa and 10 ml·min^-1, respectively. After the re-permeating hydrogen, the hydrogen permeation rate increased gradually. Finally the rate arrived at the constant value before CO was flowed. But the necessary time was depend on the concentration of CO. The necessary time for three concentration of CO 1%, 10%, and 100% were 30min, 60min, and 180min, respectively. The reason was that depositing carbon from CO affected to hydrogen permeability. The carbon was changed to methane by hydrogen flow and the membrane was recycled.

In recent years, from an environmental perspective, there has been increasing interest in the change to a sustainable society. The use of natural-fiber-reinforced biodegradable composites has been proposed as one solution. Bamboo is an often used renewable bio-resource; it has an inherent advantage of rapid growth. Polybutylene succinate (PBS), used as matrix resin, has biodegradable characteristics. This paper describes flexural properties of bamboo/PBS composites prepared by injection molding. The following results were obtained. The flexural modulus was improved with increasing bamboo powder contents when the cylinder temperature of the injection molder was 140°C. However, the flexural strength showed the opposite tendency to be decreased with increasing bamboo powder contents. An SEM photomicrograph of the fracture surface for bamboo/PBS composites showed typical fracture behavior of pull-out fibers without fiber fracture. Furthermore, there was no adhesion of PBS resin on the bamboo fiber surface. Processing conditions affected mechanical properties of bamboo/PBS composites, imparting higher flexural strength and flexural modulus at high cylinder temperatures such as 180°C and 200°C.

Potential possibility of the butyl ether (BE, oxygenates of di-ether group) was analyzed as an additives for a naturally aspirated direct injection diesel engine fuel. Engine performance and exhaust emission characteristics were analyzed by applying the commercial diesel fuel and oxygenates additives blended diesel fuels. Smoke emission decreased approximately 26% by applying the blended fuel (diesel fuel 80 vol-% + BE 20vol-%) at the engine speed of 25,000 rpm and with full engine load compared to the diesel fuel. There was none significant difference between the blended fuel and the diesel fuel on the power, torque, and brake specific energy consumption rate of the diesel engine. But, NOx emission from the blended fuel was higher than the commercial diesel fuel. As a counter plan, the EGR method was employed to reduce the NOx. Simultaneous reduction of the smoke and the NOx emission from the diesel engine was achieved by applying the BE blended fuel and the cooled EGR method.

In this study, the possibility of biodiesel fuel and oxygenated fuel (dimethoxy methane ; DMM) was investigated as an alternative fuel for a naturally aspirated direct injection diesel engine. The smoke emission of blending fuel (biodiesel fuel 90vol-% + DMM 10vol-%) was reduced approximately 70% at 2500rpm, full load in comparison with the diesel fuel. But, engine power and brake specific energy consumption showed no significant differences. But, NOx emission of biodiesel fuel and DMM blended fuel increased compared with commercial diesel fuel due to the oxygen component in the fuel. It was needed a NOx reduction counter plan that EGR method was used as a countermeasure for NOx reduction. It was found that simultaneous reduction of smoke and NOx emission was achieved with BDF (95 vol-%) and DMM (5 vol-%) blended fuel and cooled EGR method (15%).

Rotating bending fatigue tests were carried out at room temperature and 500°C for alloy 718 with nearly the same static strength but different precipitated particles, i.e. a peak aged condition (720°C-10h) and a double aged one (720°C-8h, 620°C-8h), in order to investigate the effect of precipitated particles on crack initiation and propagation behavior. Fatigue strength was higher in the double aged material than in the peak one at both temperatures. The main reason for high fatigue strength of the double aged material was that the propagation of a small crack with a few grain sizes was suppressed by the carbide particles precipitated in a grain.

The long-range aim of this research is to develop porous ceramics with high strength, excellent thermal resistance and chemical stability at high temperature in environmental industry. The C_f/SiC was made by hot pressing method with SiC powder whose particle size is 50nm and less on the average also Al₂O₃, Y₂O₃ and SiO₂ as additive. The carbon fibers of oxidation property are investigated by TGA for finding out decarburization point. As a result, decarburization point selected the specific temperature of TGA curve and the C_f/SiC composites occurred perfectly decarburization at carbon fibers so the clearly porous SiC ceramics were formed many holes of 3-5µm diameters through length direction by its reaction.

Silicon carbide (SiC) exhibits good strength at high temperatures and resistance to radioactivity. However, it has poor fracture toughness. The ability to heal cracks represents a very desirable means of overcoming this weakness. This study focuses on the crack-healing behavior and bending strength of SiC ceramics to which sintering additives have been added. Optimized crack-healing condition was found to be 1hr at an atmospheric level of 1100 °C. The maximum crack size that can be healed at the optimized condition was a semi-elliptical surface crack of 450 µm in diameter. Si oxide was revealed to be the principle material involved in crack-healing.

In the present work, a series of samples were prepared by pressureless sintering from the starting materials of Si₃N₄ (α and/or β phases), SiO₂ and Li₂CO₃. The phase transformation was studied with emphasis on the influence of sintering temperature and Li₂CO₃ content. Related phase transformation was observed and analyzed by SEM and XRD and probable mechanisms were given, which will be helpful for the further explanation to the oxidation mechanism of Si₃N₄ based ceramics at elevated temperature.

Recrystallization behavior of a nickel-base single crystal superalloy cold-deformed by compression has been investigated. The effects of plastic strain, annealing temperature and annealing time have been studied, and recrystallization diagram has been obtained. It has been found that a very strong dependence upon temperature is evident. For the single crystal superalloy with 4.5% strain, full recrystallization has been observed when annealing at 1300°C for 1h, surface recrystallization at 1250°C for 1h, cellular recrystallization at 1150°C for 1h and no recrystallization at 1100° for 1h. With the drop of temperature, the volume fraction of γ′ phase increases, which incrementally restricts recrystallized boundary migration. With the increasing of annealing time or strain, the sensitivity of recrystallization increases. Recrystallization tendency of standard- heat-treated superalloy is weaker than that of as-cast single crystal superalloy, because standard heat treatment reduces the microsegregation, lowers the eutectic amount and forms homogeneous γ1 phase distribution, which decrease preferential nucleation site of recrystallized grain and increase the resistance of boundary migration of recrystallization.

A single crystal nickel-base superalloy with ‹001› orientation was subjected to high cycle fatigue loading at temperature of 700°C and 870°C. The tests were performed in ambient atmosphere under load control at a stress ratio R=σ_min/σ_max=0.1 and a frequency of 83.3 Hz on smooth specimens. In this paper, the premature initiation and rapid propagation of cracks to failure due to high frequency cyclic loading were explored. The dislocation characteristics and fracture surface observation were evaluated through scanning electron microscopy and transmission electron microscopy, respectively. The results showed that the fatigue strength at 700°C was higher than that at 870°C. At 700°C the interaction of cyclic stress with high temperature induced the precipitation of homogeneous hyperfine secondary γ′ particles, that is beneficial to fatigue strength. At 870°C, the cyclic stress led to the formation of persistent slip bands moving through the γ matrix channels and the γ′ precipitates. The morphology change of γ′ phase was not notable during the deformation at high frequency cyclic loading.

Total strain controlled low cycle fatigue tests were conducted at 1173K for DD32 and SRR99 alloys. With the increase of total strain range, the stress amplitude of DD32 alloy improved more fleetly than that of SRR99 alloy. At total strain ranges less than or equal to 1.0%, the low cycle fatigue life of DD32 alloy was greater than that of SRR99 alloy. It was shown that the higher content of refractory elements in DD32 alloy resulted in a remarkable improvement of LCF properties compared to SRR99 alloy. The crack propagation perpendicular to the stress axis occurred in transgranular mode in both alloys. DD32 alloy presented more ductile character than SRR99 alloy.

Effects of different ratios of Ni to Al on the ductility and toughness of Ni_33+xAl_28-xCr₃₀Mo₄Nb₅ (x=0, 6, 9, 12) alloys are investigated. High temperature compression test is also conducted. The results show that with ratio of Ni to Al up to 1.77, γ phase precipitation result in ductility and fracture toughness enhanced at room temperature. The reinforced Cr₂Nb-type phase and γ phase benefit for the high temperature strength and room temperature ductility, respectively.

The microstructures of the FeNiCr-TiC composite produced by the rapid solidification thermite process were investigated using X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The effects of aging treatment on the microstructure and fracture toughness of the composite were examined. Results showed that the FeNiCr-TiC composite was composed of ferrite (α-FeNiCr), TiC and NiAl (β phase). TiC particles in the matrix were in the shape of polygon and uniformly distributed, and their size was less than 3 µm. The β phase was coherent with the ferrite matrix, and its average size was about 50 nm. The fracture toughness of composite was 22 MPa·m^1/2 without aging. When the aging temperature was below 600°C, the fracture toughness of the composite had higher plateau values and reached the maximum of 32 MPa·m^1/2 at aging temperature 500°C due to the precipitation of NiAl phase on the nanometer scale. The fracture toughness decreased rapidly aged at 650°C, and then kept homology value in the range of 700 to 900°C, which was attributed to the precipitation of needle-shaped carbide (Cr/Fe)₇C₃ at the grain boundaries.

Three Al₂O₃/SiC composite ceramics were prepared, which included 1, 3 or 5 wt. % Y₂O₃, and their high-temperature bending strengths and in-situ crack-healing behaviors examined. A surface elliptical-crack of about 100 µm in diameter was introduces on the specimens using a Vickers hardness indenter. From in-situ observations, the Al₂O₃/SiC composite ceramic with 3 wt.% Y₂O₃ showed superior crack-healing ability than the 1 and 5 wt.% Y₂O₃ ceramics. The as-cracked specimen with 3 wt.% Y₂O₃ showed strength recovery on healing for 1 hr at 1473 K in air, which may have been due to the lower crack-healing temperature on the addition of 3 wt.% Y₂O₃. The heat-resistance limit temperatures of the crack-healed Al₂O₃/SiC composite ceramics were 1073, 1373 and 873 K for 1, 3 and 5 wt.% Y₂O₃, respectively.

The characterization of liquid phase sintered(LPS) SiC based materials has been investigated with the analysis of microstructure and flexural strength. Especially, LPS-SiC materials were examined for the variation of test temperature and composition ratios (Al₂O₃,/Y₂O₃) of sintering additives. LPS-SiC based materials were fabricated by hot pressing(HP) associated with the liquid phase formation of sintering additives(Al₂O₃,Y₂O₃). LPS-SiC_f/SiC composites were also fabricated with plane-woven(PW) Tyranno-SA fibers without an interfacial layer. LPS-SiC materials showed a dense morphology with the creation of the secondary phase like YAG. The composition ratio of sintering additives led to the variation of sintered density and flexural strength. The flexural strength of LPS-SiC materials was greatly decreased at the temperature higher than 1000°C. LPS-SiC_f/SiC composites represented an average flexural strength of about 260 MPa, accompanying the catastrophic fracture behavior without any full-out phenomena.

This paper dealt with the thermal shock damages of MoSi₂ intermetallics by a nondestructive technique. The flexural strength of MoSi₂ intermetallics depending on the thermal shock cycles has been also investigated. The thermal shock test was repeatedly performed up to 80 cycles at the temperature difference of 423 K. The flexural strength of MoSi₂ intermetallics decreased with the increase of thermal shock cycle, due to the creation of crack and its propagation. MoSi₂ intermetallics represented the drastic reduction of ultrasonic wave velocity at the thermal shock of 40 cycles. The attenuation coefficient of MoSi₂ intermetallics increased with increasing the thermal shock cycle due to the activation of damage degree

Silicon carbide (SiC) materials have been extensively studied for high temperature components in advanced energy system and advanced gas turbine. The SiC ceramics have been fabricated by a NITE (Nano Infiltration Transient Eutectic Phase) Process, using Nano-SiC powder. The sintering additives used for forming liquid phase under sintering process, used the sintering additives ratios were an Al₂O₃-Y₂O₃ system or add SiO₂ contents. A major R&D focus for the SiC ceramics is the production to obtain high purity SiC ceramics. In this study, we investigated roles of the sintering additives(Al₂O₃:Y₂O₃) to fabrication of the SiC ceramics. The effects of SiO₂ contents and density properties of the SiC ceramics were also investigated. To investigate the effects of SiO₂, Al₂O₃/Y₂O₃ composition were fixed and then SiO₂ ratios were changed as several kinds, and to confirm the effects of sintering additives ratios (Al₂O₃:Y₂O₃) they were changed between 4:6 and 6:4 in x wt.%.

The use of silicon-based ceramics and composites as combustor liners and turbine vanes provides the potential of improving next-generation turbine engine performance, through lower emissions and higher cycle efficiency, relative to today's use of super alloy hot-section components. As a series of research for FOD resistant, a particle erosion wear test was carried out for continuous Pre-SiC fiber-reinforced SiC matrix composites with a new concept of lab. scale fabrication by LPS process. The result shows that aperture (some form of porosity) between fiber and interface has a deleterious effect on erosion resistance. Aperture along the fiber interfaces consequently causes a severe wear in the form of fiber detachment. Wear rate increase proportional as contents of open porosity increases. For nearly full dense composite materials of about 0.5 % porosity, are about 200 % more wear-resistant than about 5 % porous composites. Grain growth and consolidate condition of matrix which directly affects to FOD resistant are also discussed.

This paper dealt with the effect of different induction melting technologies on mechanical properties of Nb-16Si-22Ti-2Al-2Hf-17Cr alloy. The cast ingots were fabricated first by arc-melting, and then remolten in the vacuum induction furnace. The results showed that the ingot with refining process of 1800°C/15min and 0.1 at% C addition had finer microstructure and higher room-temperature fracture toughness. In addition, the compressive strength of the ingot with refining technology of 1700°C/10min was 315MPa at 1250°C. However, the arc melting ingot had the lowest fracture toughness and high-temperature compressive strength.

The effects of cooling rate and pouring temperature on microstructure and fracture toughness of the induction melted Nb-16Si-22Ti-2Hf-2Cr-2Al alloy were extensively investigated. The results revealed that with the decrease of cooling rates, the Nb_ss exhibits the dendrite-like morphology, the primary Nb₅Si₃ blocks form and the mean sizes of Nb₅Si₃, Nb_ss and eutectic colonies increase; with the increase of the pouring temperature, the microstructure shows columnar structure and the particles of Nb₅Si₃ or Nb_ss become long and thin. Pouring temperature and cooling rate had little influence on the volume fractions of Nb_ss and Nb₅Si₃ and their compositions. The Nb₃Si phase eliminated in the case of high pouring temperature and slow cooling rate. Fracture toughness of the alloy prepared by induction melting is on the order of 13.7 to 15.3 MPa·m^1/2. Similar fracture toughness value of each slab may be ascribes to the same volume fraction of the Nb_ss.

The effect of the crystal orientation on the stress rupture behavior of the Ni₃Al-base Single Crystal alloy IC6SX under the test condition of 1100°C/120Mpa has been studied. The results showed that the stress rupture lives of the specimens with [001], [011] and [111] crystal orientations were 205.45h, 268.6h and 485h, respectively, i.e., the specimen with [111] crystal orientation had the longest stress rupture life. The results of the tests also showed the significant different of high temperature stress rupture elongation and area reduction for different crystal orientation specimens, i.e., the ruptured elongations for the specimens with [001], [011] and [111] crystal orientations were 61.9%, 22.9% and 28.8%, and the values of area reduction for the specimens with [001], [011]and [111] crystal orientations were 11.7%, 12.2%and 7.3% respectively.

Practical residual strain field around the microcrack tip of fully lamellar γ-TiAl alloy was estimate the by digital image correlation (DIC) technology with in-situ SEM observation. And the macro plastic deformation before fracture of such low ductility alloys was observed. The results showed that the size of plastic zone around microcrack tip was 2 ~ 10µm which was much more smaller than the calculated value by fracture mechanics. During the magnified observation on the plastic deformation region, a series of microcracks were observed in the specimen without macro cracking. Furthermore, the size of distribution region of the microcracks were in the same order of magnitude with the calculated plastic zone near primary crack tip which just reflected the comprehensive effect of microcracks and the plastic deformation on the tips of them.

Nb-xSi(x=3,9,16)-22Ti-3Cr-3Al-2Hf (at.%) have been successfully prepared by directional solidification in an optical floating zone furnace. Microstructure analysis and phases identification of the alloys were examined by X-ray diffraction (XRD), Electro Probe Micro Analyzer (EPMA) and Energy Disperse Spectroscopy (EDS). Fracture toughness specimens without pre-crack were prepared, room temperature fracture toughness of alloys was tested by three-point bending method, and fracture mechanism was studied. The results showed that with increasing Si content, Nb₅Si₃ phase gradually increased and the phase transformed from γ-Nb₅Si₃ to the stable α-Nb₅Si₃ phase and β-Nb₅Si₃ phase. There appeared the Ti-rich Nb₅Si₃ phase when the Si content is 16 at%. In addition, more micro-cracks generated in the Ti-rich Nb₅Si₃ phase, which seriously affected room temperature fracture toughness of the alloys.

The mechanical properties of Ti-48Al-2Cr-2Nb alloy were discussed after the high temperature corrosion tests carried out with salt mixture of 75wt. % Na₂SO₄ and 25wt. % NaCl at 800°C. The microstructure of the alloy after corrosion was observed by SEM and the fracture behavior of the corroded and uncorroded alloys was investigated by means of the three-point bending tests. It has been shown that the corrosion path was mainly along the lamellar structure and rough surface with a large number of corrosion pits formed during the high temperature corrosion. The experimental results also indicated that the bearing capacity of bending fracture descended evidently due to the molten salt corrosion at high temperature, which only had remarkable effects on the surface state of the alloy. The microcracks inside the alloy always propagated along the phase interfaces and grain boundaries while the corrosion pits on salt-deposited surface became the main crack initiation location in corroded alloy. The stress concentration caused by corrosion was considered as the essential reason of the property reduction, which decreased the energy barrier of crack nucleation and shortened the incubation period.

Multi-layer diamond-like carbon (DLC) coating, 150 and 220 nm thick were deposited by negative pulsed d.c. bias induced with magnetron sputtering. The objective of this research is to resolve a wear resistance in terms of DLC coating residual stress and mechanical properties. The bias was controlled from - 200 to 0 V during 10 second with point contacting controller. The surface structure was continuously fabricating to soft and hard-layer during deposition. It was shown that the compressive residual stress and hardness were 0.09, 18 GPa under multi-layer coating condition. The as-deposited DLC coating has a relatively higher wear resistance than unmodified DLC under nanoabrasive wear. It also showed that multi-layer DLC coating had no wear until 400 nN. The decreased residual stress and increased film hardness in the multi-layer coating gave a rise to increase wear resistance.

This paper reviews several innovative techniques that have been developed in our labs to overcome the shortages of conventional sol-gel techniques, and discusses the technical details of preparing these ceramic coatings with controllable thickness, microstructure, composition and improved properties.

P-type (Al, N) co-doped ZnO films have been prepared by thermal oxidation of sputtered Zn₃N₂:Al precursor films. The Zn₃N₂:Al precursors are deposited by RF magnetron sputter and then annealed in oxygen atmosphere at different temperatures. The doped ZnO films are characterized by XRD, XPS and Hall effect measurement. The results indicate that the ZnO films only show p-type conductivity with an annealing in a temperature window: ZnO films show the best p-type characteristics with a hole concentration of 4.2 × 10¹⁷cm^-3, mobility of 0.52 cm/V.s and resistivity of 28Ωcm after an annealing at 550°C. Using these p-type ZnO films, ZnOp-n junctions are prepared which show good diode characteristics. The chemical states of N and Al dopants in the ZnO host material are investigated by XPS method after annealing at different temperatures; and the doping mechanisms are discussed based on the XPS results.

Silicon incorporated diamond-like carbon films up to 6.2 at. % (DLC-Si) were deposited onto a high speed steel samples by using a radio frequency plasma-enhanced chemical vapor deposition method. The influence of silicon doping on chemical composition, bonding structure, hardness, and adhesion of DLC films was investigated. Hexamethyldisilane (HMDS) gas was used as a silicon source with Ar carrier gas ranging from 0 to 15 sccm. Also, the mixtures of methane (CH₄) and Ar gases were used as precursor gases. The addition of silicon into the DLC film was found to lead an increase of bonding ratio (sp³/sp²), hardness and critical adhesion

To investigate the possibility of developing a new surface modification method by the combined process of ELID grinding and high-temperature oxidization, we treated ELID finished specimens and polished specimens by high-temperature oxidization in the atmosphere and performed detailed analysis to determine how the treatment would change the specimen surfaces. The ELID-series showed high quality surface roughness and excellent tribological characteristics as compared with the polished-series. The improved surface properties of the ELID-series seem to result from formation of fine, uniform structures of spinel-type multiple oxides FeCr₂O₄ and Cr₂O₃ on the surface by high-temperature oxidization.

Ultrasonic nanocrystal surface modification (UNSM) has applied to a radial journal bearings made of bearing steel SUJ2. Mechanical characteristics are compared between UNSM treated and untreated bearings. Friction torque is measured at the boundary lubrication condition, the mixed lubrication condition, and the full hydrodynamic lubrication condition. The peak torque at the boundary lubrication condition and the transition period to mixed lubrication condition on the UNSM treated samples are reduced. These effects are very useful to improve the service life of journal bearings. The Stribeck curve at the mixed and full hydrodynamic lubrication is derived and compared. The friction coefficient at these two regimes is reduced by more than 50%, which will do effective role for improvement of energy efficiency. The major effects for this reduction at three lubrication regimes could be explained in the terms of micro dimple surface.

Plasma-sprayed YSZ coatings have been widely employed as thermal insulation coatings in gas turbine for its low thermal conductivity. Thermal conductivity of ceramic coatings is closely related to coating microstructure. In the present study, YSZ coating was deposited on a stainless steel by atmospheric plasma spraying using a fuse-crushed 8wt.%Y₂O₃-stablized ZrO₂ powder at different spray distances from 70 mm and 100 mm. The microstructure of YSZ coatings was quantitatively characterized through visualization of lamellar structure assisted by electroplating Ni and subsequent EDX line analysis. The thermal conductivity of YSZ coatings with different microstructures was tested by a laser flash technique. Results showed that the mean lamellar bonding ratio was 32% and almost kept unchanged for the coatings deposited at 70 mm and 85 mm and it was reduced by 25% when distance was increased to 100 mm. The thermal conductivity of the coatings largely depended on the mean bonding ratio between lamellae and increased with the bonding ratio.

This study aims at investigating the wear behavior of thermally sprayed Ni-based self-flux alloy coatings against different counterparts. Ni-based self-flux alloy powders were flame-sprayed onto a carbon steel substrate and then heat-treated at temperature of 1000 °C. Dry sliding wear tests were performed using the sliding speeds of 0.2 and 0.8 m/s and the applied loads of 5 and 20 N. AISI 52100, Al₂O₃, Si₃N₄ and ZrO₂ balls were used as counterpart materials. Wear behavior of Ni-based self-flux alloy coatings against different counterparts were studied using a scanning electron microscope(SEM) and energy dispersive X-ray spectroscopy (EDX). It was revealed that wear behavior of Ni-based self-flux alloy coatings were much influenced by counterpart materials.

The wetting behavior of Ti-78Cu and Ti-50Cu alloys on graphite has been investigated by the sessile drop method in high vacuum. The contact angle of Ti-Cu alloys on graphite is influenced by the wetting temperature. The wetting of Ti-78Cu and Ti-50Cu alloys on graphite is chemical wetting. The microstructure and composition of the interfacial zone of the wetting samples were analyzed by SEM, EDX and XRD. Microstructure and phase analysis reveals that inter-diffusions and interfacial reactions take place in the wetting process. The reaction products include TiC and the intermetallic compounds composed of Ti and Cu. The inter-diffusions and interfacial reactions contribute to the interfacial bonding.

Self-formation of MgO or Al₂O₃ surface layer on CuMg or CuAl alloys by annealing in H₂ gas was investigated theoretically and experimentally. Theoretical consideration shows that Mg or Al can segregate to the surface of Cu during the annealing, while the enrichment ability is much stronger for Mg. Meanwhile, the MgO or Al₂O₃ surface layer is self-formed by the preferential reaction of Mg or Al with O₂ remnant in H₂ atmosphere. The Al₂O₃ surface layer is expected to play a role in passivating the surface of Cu. However, the MgO layer would suffer failure in passivating the surface due to incorporation of Cu and fissures formed in MgO during the annealing process. Our theoretical predictions are in agreement with experimental observations.

Commercially available, gas-atomized NiCrAlY powder was milled in Ar atmosphere to prepare nanostructured powder. The NiCrAlY coatings in the conventional microstructure and the nanostructure were subsequently deposited by cold spraying using the as-atomized powder and milled powder. The influence of the powder structure on the microstructure of cold-sprayed coating was investigated. It was found that dense NiCrAlY coatings can be cold-sprayed using two powders. Isothermal oxidation was performed at 1000°C in air for up to 500 hours. The results showed that the growth rate of the oxide on the nanostructured NiCrAlY coating was almost comparable to that of the conventional NiCrAlY coating. A uniform Al₂O₃ layer was formed on the surface of the nanostructured coating surface. Moreover, a dual-subscale oxide was formed on conventional coating composing of an inner Al₂O₃ oxide and an external mixed oxide.

In this study, the peening behavior of shot particles in a fine particle peening (FPP) process such as velocity and impact angles were analyzed by using a high-speed-camera. Results showed that the velocity of shot particles depended on a peening pressure; the higher the peening pressure, the higher the particle velocity. The particle velocity measured in this study was approximately 120 m/s; this was much higher than that of the conventional shot peening (SP) process. This was because the air resistance of shot particles in the FPP process was higher than that of shot particles in the SP process. In order to discuss the surface modification effect of the FPP process, commercial-grade pure iron treated by the FPP process was characterized by micro-Vickers hardness tester and scanning electron microscope (SEM). Thickness of hardened layer treated with higher peening pressure was much higher than that of the lower pressure treated one. The unique microstructure with stratification patterns, which was harder than that of the other part, was observed near the specimen surface. The reason for the microstructural changes by the FPP treatment was discussed based on the kinetic energy of shot particles.

Lead-free piezoelectric (Bi_1/2Na_1/2)TiO₃ (abbreviated as BNT) films were deposited on 0.2 mm thick pure titanium(Ti) substrates by a hydrothermal method. Scratch tests and Vickers indentation tests were performed to quantitatively assess the adhesion strength between BNT films and Ti substrates. Some of Ti substrates were pretreated by chemical polish and mechanical polish respectively prior to BNT film deposition with a view of investigating the effects of substrate surface pretreatments on the adhesion of BNT films. In the scratch test, the critical force was determined from the variations of the tangential force and the acoustic emission (AE) signals with the normal force. The scratch test results revealed that the chemical polish pretreatment effectively improved the adhesion of BNT films. In addition, the critical substrate strain inducing the adhesion failure of BNT films has been investigated by the Vickers indentation test combined with finite element analysis (FEM).

In this paper, a novel hemispherical microbond specimen is proposed for evaluating the interfacial shear strength of fiber-reinforced composites. A hemispherical microbond specimen was developed with the insertion of a pin-holed, Teflon film into a droplet matrix surrounding a single fiber. This experimental test offered more reliable strength data in the hemispherical specimen. Thus, the hemispherical microbond specimen is recommended to be suitable for evaluation of interfacial shear strength as a convenient alternative for the cylindrical pull-out test.

UNSM(Ultrasonic Nanocrystal Surface Modification) technology has been applied to test specimens of bearing rings and rollers made of SAE52100. Mechanical properties, especially rolling contact fatigue characteristics, are analyzed using two-roller test and 6-ball test before and after UNSM treatment. The main effects to improve rolling contact fatigue characteristics by UNSM treatment are explained in the view points of residual stress, hardness and surface topology.

To improve the atomic oxygen (AO) erosion resistance of the polyimide (PI) maretials, cage-shaped poly-γ-aminopropylsiloxane (NPOSS) was synthesized from γ-aminopropyltriethoxysilane through the control of hydrolytic condensation conditions. Poly-γ-aminopropylsiloxane/methylphenylsilicone (NPOSS/MPS) hybrid films were prepared on PI samples. The physics and chemistry properties of the hybrid films surface was analyzed after exposure to AO flux in a ground AO simulated facility. The results showed that: NPOSS gathered to the spherical shapes and uniformly distributed in films, SiO₂ layer formed on the films surface after explorer and prevented the further AO erosion, mass loss and erosion rate of samples was dramatically decreased, AO erosion resistance had been increased and it could be further enhanced with the increase of NPOSS content.

The corrosion behavior of anodized film on AZ91D magnesium alloy in 3.5% neutral NaCl solution was investigated by saline immersion test. The results show that new corrosion points seldom occur on the surface of the said anodized film during the immersion time in 3.5% NaCl neutral aqueous solution after the first macroscopic corrosion point appears on the anodized film, while the previous corrosion point extends vertically or horizontally and turns into a corrosion pit which is in form of "strip". Moreover, the corrosion occurs firstly on α phase rather than β phase, when the corrosion of anodized film reaches the Mg alloy substrate. The corrosion products of anodized film on AZ91D magnesium alloy in neutral immersion solution were analyzed by XRD. A possible corrosion reaction and model about the corrosion of anodized film on AZ91D magnesium alloy in NaCl solution based on the experimental results is proposed.

Electrochemical measurement and surface analysis methods were employed to investigate the Microbiologically Influenced Corrosion (MIC) influenced by Thiobacillus ferrooxidans biofilm. Electrochemical impedance spectroscopy (EIS) results indicated that the impedance value of steel A3 after 21 days of immersion in sterile solution was much higher than that of T.f solution. Atomic Force Microscopy (AFM) results showed the adsorption state of the microorganism on the metal surface for 7 days of exposure in T.f solution. The morphologies of the surface film were analyzed with the Scanning Electron Microscope (SEM), which showed the changes with exposure time of the film on the metal surface. The special morphology and the heterogeneity of Thiobacillus ferrooxidans biofilm induced the localized corrosion of steel A3. After 21 days of exposure, general corrosion occurred in the sterile solution, while localized corrosion was detected under the effect of Thiobacillus ferrooxidans.

Biological materials naturally display an astonishing variety of sophisticated nanostructures that are difficult to obtain even with the most technological advanced synthetic methodologies. We describe a new type of Co-Ni-P ternary alloy microstructure particles prepared by electroless deposition based on biological templating. The plating parameters were explored and the microstructure material was studied by microbiological method, scanning election microscope (SEM), energy dispersive analysis (EDS), X-ray diffraction (XRD) and vibrating sample magnetometer (VSM). The results showed that the Bacillus were coated by Co-Ni-P ternary alloy successfully and the average contents of Co, Ni, and P in Co-Ni-P coating were about 18.73 wt%, 74.43 wt% and 3.04 wt%, respectively. The structures of as-plated Co-Ni-P alloy were amorphous and exhibited excellent magnetic property. The values of saturation magnetization (Ms), remnants magnetization (Mr) and coercivity (Hc) of the sample were about 18 emu/g, 3.5 emu/g, and 107 Oe, receptivity.

The surface properties like roughness etc. strongly influence the fatigue strength of high-tensile steel. To investigate the effect of surface condition and TiN coating on the fatigue strength of high-strength steel, four-point bending fatigue tests were carried out for martensitic stainless steel with TiN film coated using arc ion plating (AIP) method. This study, using samples that had been polished under several size of grind particle, examines the influence of pre-coating treatment on fatigue properties. A 2-µm-thick TiN film was deposited onto the substrate under three kinds of polishing condition. The difference of the hardness originated in the residual stress or thin deformation layer where the difference of the size of grinding particle of the surface polishing. And it leads the transformation of the interface of the substrate and the TiN film and improves fatigue limit.

In this study, a system for non-contact in-situ measurement of strain during tensile test of thin films by using CCD camera with marking surface of specimen by black pen was implemented as a sensing device. To improve accuracy of measurement when CCD camera is used, this paper proposed a new method for measuring strain during tensile test of specimen with micrometer size. The size of pixel of CCD camera determines resolution of measurement, but the size of pixel can not satisfy the resolution required in tensile test of thin film because the extension of the specimen is very small during the tensile test. To increase resolution of measurement, the suggested method performs an accurate subpixel matching by applying 2nd order polynomial interpolation method to the conventional template matching. The algorithm was developed to calculate location of subpixel providing the best matching value by performing single dimensional polynomial interpolation from the results of pixel-based matching at a local region of image. The measurement resolution was less than 0.01 times of original pixel size. To verify the reliability of the system, the tensile test for the BeNi thin film was performed, which is widely used as a material in micro-probe tip. Tensile tests were performed and strains were measured using the proposed method and also the capacitance type displacement sensor for comparison. It is demonstrated that the new strain measurement system can effectively describe a behavior of materials after yield during the tensile test of the specimen at microscale with easy setup and better accuracy.

This paper describes the influence of surface roughness on the mobility of a-SiN:H and a-Si:H. For the a-SiN:H deposited by PECVD, the roughness was 0.832 nm. The a-SiN:H layer composed of (PECVD 150 nm + RACVD 100 nm) had better characteristic of roughness than the a-SiN:H layer (PECVD 250 nm) by 47%. The roughness of the a-Si:H (PECVD 200 nm) deposited on the a-SiN:H layer was 0.803 nm. And the roughness of a-Si:H (RACVD 100 nm + PECVD 100 nm) deposited the a-SiN:H layer is better than the a-Si:H (PECVD 200 nm) by 27%. After depositing the layer of a-SiN:H and a-Si:H at the best condition obtained by the experiments the mobility was measured. The a-Si:H is deposited by the PECVD, the obtained mobility was 0.218 cm ²/V ·sec. The a-Si:H was deposited by the PE/RACVD, the obtained mobility was 0.248 cm ²/V ·sec. The mobility is enhanced by 10% by depositing the a-Si:H layer using the PE/RACVD method.

We investigated the surface fatigue crack behaviors including initial surface crack appearances depend on three artificial notch lengths applied with the axle load level of the maximum load, 1,103 MPa and minimum load 55.3 MPa at the stress ratio of 0.05. This load level is the F100 engine's maximum operation condition of Waspaloy. The initial cracking site in depth is started from multi-origin. The effectiveness of crack growth rate by ductile striation space measurement on the fractured surface is confirmed by the working load and the stress intensity factor range. The surface cracks of Waspaloy at room temperature in air follow the ΔK vs da/dN and db/dN relation, even though the crack length initiated early in notch size 1 mm and initiated very late in notch size 4 mm. And the ΔK vs da/dN and db/dN relation have similar slope at 3 kinds of notches.

The electroformed copper with various microstructures are fabricated under conditions of non-agitation and ultrasonic agitation according to the demand of the electroforming micro components. The microstructure of the electroformed copper layer was observed by optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The preferred orientations of the layer were characterized by X-ray diffraction (XRD). The tensile strength was evaluated with a tensile tester. It was found that the copper layer preferentially grow along the (220) plane during the electroforming process, and the ultrasound-assisted technique led to a highly preferred orientation. The effects of ultrasonic vibration increased the chance of nucleation and controlled the excessive growth of copper grains during electroforming process. The microstructure of copper electroformed under condition of ultrasonic agitation is made up of regular columnar crystals, and its tensile strength increased by 40% in comparison with that of under condition of stationary state.

The shell material of microcapsules has an important effect on the electrolytic co-deposition behavior, the release of core material and the surface performance of composite coating. This paper discussed the tensile property and the stability of three shell materials including polyvinyl alcohol (PVA), gelatin and methyl cellulose (MC). It is found that these three shell materials have good mechanical strength and flexibility which are favorable to electrolytic co-deposition and stability of microcapsules in composite coating and that MC has well permeability and porosity which has a positive effect on the release of the core material in composite coating. Moreover, the study of the thermal properties and water vapor permeability of the three shell materials showed that their permeability improved with increase of temperature and humidity. In addition, the composite copper coating containing microcapsules with PVA, gelatin or MC as shell material was prepared respectively.

Ti-Al-N Films with large scale chemical composition were fabricated on stainless steels by changing the relative substrate positions to targets using double-targeted reactive magnetron sputtering technique in one same process. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to characterize the composition and microstructure of films. Tribological performance of films was test at room temperature in air without any lubricant. Chemical composition of films altered with substrate positions from Ti_0.82A_10.18N to Ti_0.12Al_0.88N. XRD results indicated that before heat treatment sputtered films were amorphous, but different phases such as TiN, AlN and TiAlN were formed in films with different composition after heat treatment of 700°C × 1h. Friction and wear tests indicated that films with x = 0.57, 0.65 hold the best tribological performance of Ti-Al-N films system because of the formation of hard phase TiAlN and different wear mechanism.

In this study, the interfacial perpendicular crack behavior and stress state of the unidirectional fiber reinforced Metal Matrix Composites (MMCs) are investigated by using FEA under the transverse loading. The fiber assumed as isotropic linear elastic SiC and the matrix is assumed as isotropic elastic-plastic Ti. The fiber/matrix interface is modeled as multi thin layer with different linear material properties. The behavior of perpendicular crack to the interface according to the change of the interface characteristics and thickness are evaluated.

β-NiAl as a promising oxidation resistant coating material due to it high melting point and good oxidation resistant, however it reveals poor cyclic oxidation performance. In this paper, reactive element Dy doped β-NiAl coatings were prepared by electron beam physical vapor deposition (EB-PVD). Dy doping led to the grain refinement microstructure and Dy segregated mainly at grain boundaries. Cyclic oxidation behaviors of the coatings at 1100°C were investigated. The 0.05at.% Dy and 0.1at.% Dy doped coatings exhibited lower oxidation rate and better cyclic oxidation performance, as compared to the undoped coating. The effects of Dy addition on the morphologies and growth mechanism of the oxide scale were discussed.

NiAl has attracted increasing attentions because of its promising potential as protective coating materials for high temperature oxidation resistance. In this paper, Dysprosium (Dy) doped NiAl alloys were produced by arc melting. Cyclic oxidation of the alloys was carried out at 1200°C. The effects of Dy as a reactive element on the microstructure and failure of alumina scales on NiAl were investigated. For the melted alloy, Dy was mainly precipitated along the grain boundary and some within the grains in the form of DyNi₂Al₃ phase. Compared to Al₂O₃ scale formed on the undoped NiAl alloy, the microstructure of the scale was greatly changed and the ridge-like Al₂O₃ scale became less distinct on Dy-doped NiAl. The equi-axed alumina scale grew on NiAl, whereas the columnar alumina developed on Dy doped NiAl. The Dy dopant prevented the oxide scale from rumpling and the formation of cavities beneath the oxide scale. Due to this, the oxide scale adhesion was significantly improved. For Dy-doped NiAl, the scale failure mostly occurred surrounding the oxide protrusions where were rich in Dy.

The bare superalloy DZ 125 alloy, the aluminide coated specimens and electron beam physical vapor deposited (EB-PVD) thermal barrier coating (TBC) consisting of yttria stabilizied zirconia (YSZ) topcoat and NiCoCrAlY bond coat specimens were exposed to atomized seawater and kerosene at 900°C and the cyclic hot-corrosion behaviors of the specimens were investigated. Disastrous spallation of the bare superalloy occurred within 50 h hot-corrosion. In contrast to this, after 100 h hot-corrosion, the average mass change for the aluminized and TBC coated specimens is 0.7 mg/cm² and 0.63 mg/cm², respectively, exhibiting excellent hot-corrosion resistance.

The durability and reliability of thermal barrier coatings(TBCs) have become a major concern of hot-section components due to lack of a reliable life prediction model. In this paper, it is found that the failure location of TBCs is at the TBC/TGO interface by a sequence of crack propagation and coalescence process. The critical crack length of failure samples is 8.8mm. The crack propagation rate is 3-10µm/cycle at the beginning and increases largely to 40µm/cycle near coating failure. A life prediction model based a simple fracture mechanics approach is proposed.

Diffusion experiments on Nb/Si couples were conducted at 1050°C, 1150°C, 1250°C for annealing for 8h, 10h and 15h. Two intermediate phases, NbSi2 and Nb5Si3, were found to develop and grow as parallel layers in the Nb/Si couples, according to the parabolic rate law. The diffusion properties of the different phases were evaluated in terms of alternative theories, which were demonstrated to be equivalent algebraically but complementary because they are expressed in terms of different experimental variables.

A Mo(Si,Al)₂ coating is developed to protect Nb_ss/Nb₅Si₃ in situ composite by plasma spraying. The binary layers of this coating consist of an inner interdiffusion layer surrounded by Mo(Si,Al)₂ layer with C40 crystal structure. After oxidation at 1250°C for 100h, Mo(Si,Al)₂ coating exhibited an excellent protection against oxidation and good adherence to substrate. The oxidation curve followed parabolic law and even after oxidation at high temperature for 100h, the weight gain per unit area of Mo(Si,Al)₂ coating is 8.24mg/cm². No evident spalling of coating to substrate was observed but a continuous and compact layer of Al₂O₃ was formed on coating surface to prevent oxidation below coating and substrate.

The starting nano-TiO₂ feedstock was agglomerated by spray-drying process. Nano-TiO₂ coatings on transparent glasses were prepared by atmospheric plasma spraying (APS). The variation of the anatase content, porosity and grain size with the arc current is investigated extensively. Result shows that the nano-TiO₂ phase is composed of anatase and rutile phase. The content of anatase in the sprayed coatings decreased and the grain size increased with the arc current increasing, and the porosity first increased and then decreased. As-sprayed nano-TiO₂ coatings obtained at the spraying current of 400 A have the best photocatalytic property due to the synergistic effect of the fractions of anatase phase and the rate of porosity.

A nickel-base superalloy has been used to deposit the aluminide coating by low-temperature pack cementation process. The high temperature oxidation tests on aluminized alloys and the uncoated specimens are carried out at 1000°C for 10h. It is observed that a dense and protective Al₂O₃ surface layer is produced on the aluminized alloy, and the aluminizing process has greatly enhanced the high temperature oxidation resistance of the Ni-base superalloy at 1000°C. As a contrast, the uncoated specimen begins to be failure when treated only for 6h at the same temperature.

Black and gray microarc oxidation coatings have been obtained on 2A70 Aluminum alloy in phosphate electrolyte with and without titania sol, respectively. The growth process of the microarc oxidation coating in the electrolyte with titania sol was investigated. The coating was characterized by scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and X-ray. The coating thickness was measured by eddy current thickness meter. The results show that the titania sol increase the growth rate of microarc oxidation coating. In both cases the composition of coatings contain Al and O, and are mainly composed of γ-Al₂O₃ and AlPO₄. Compared with the gray coating, large amount of Ti is found on the surface of black coating. The titania sol added in the electrolyte results in Ti in the coating, in the form of TiO and Al₂TiO₅.

The effects of the reducing agents of hydrazine (H₄N₂), sodium borohydride (NaBH₄), and triethylsilane (C₆H₁₅Si) on the morphologies of gold nanoparticles in the poly(styrene-b-4-vinylpyridine) micelle were studied using small-angle X-ray scattering (SAXS), UV/visible spectroscopy and transmission electron microscopy (TEM). "Cherry" morphology was found in the gold nanoparticles reduced by hydrazine while "raspberry" morphology was found in the gold nanoparticles reduced by sodium borohydride. Hydrazine was more effective in reducing gold nanoparticle in the core of the PS-b-P4VP micelle than sodium borohydride and triethylsilane. The nanoparticles reduced by hydrazine were confined in the core and more regular than those reduced by sodium borohydride and triethylsilane. The possible mechanism leading to these morphological differences was also discussed.

The effect of Al content on the self-propagating high-temperature synthesis (SHS) reaction among Al, TiO₂ and B₂O₃ was experimentally investigated. The Al content plays an important role in controlling the reaction behaviors. With the increase in reactant Al, the maximum combustion temperature decreases, the propagating wave velocity first increases and then decreases, while the ignition delay time shows an opposite tendency. More importantly, the increase of the Al content in the reactants has an insignificant effect on the phase constitutions of the synthesized products but reduces the size of the synthesized TiB₂ particles.