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This paper presents the development of an innovative numerical decision-making model aimed at identifying the optimal combination of process parameters during friction stir welding (FSW) of dissimilar AZ31B magnesium (Mg) and AA6082 aluminum (Al) alloy plates. The study considered not only the tool’s traverse speed and rotational speed as input parameters but also the positioning of the AZ31B Mg alloy on either the advancing side (AS) or the retreating side (RS). A total of 21 experimental runs were conducted, with tensile strength, elongation percentage, impact energy, and hardness evaluated as performance outcomes. In the first phase, a multi-criterion decision-making (MCDM) methodology was employed to develop the numerical model and identify the ideal set of parameters. To ensure the model’s reliability and accuracy, a sensitivity analysis was conducted. The results obtained from the MCDM model were validated by comparing them with those derived from a fuzzy logic-based decision-making approach. In the second phase, a response surface methodology (RSM) was applied to construct a numerical model using multivariate regression. A trade-off analysis, utilizing a multi-objective RSM approach, was performed to optimize the parameter combination. The optimal solution, computed through this approach, was further validated via a confirmation experiment. The ideal combination of process parameters — rotational speed of 841.42rpm, traverse speed of 0.5mm/s, and positioning of AZ31B Mg alloy on the advancing side — yielded a tensile strength of 214.65MPa, elongation of 10.76%, hardness of 74.89HV, and an impact energy of 6.01J. This research paper demonstrates the effectiveness of the proposed hybrid MCDM-RSM model in accurately determining the optimal FSW parameters and highlights its potential application in similar joining processes.

In this paper, the mechanical properties and microstructure of AZ31 and AA3105 joints obtained from single-pass friction stir welding are investigated. The microstructure of the weld has been analyzed by optical and scanning electron microscopy (SEM) to investigate the tunnel and volumetric (wormhole) defects, as well as the distribution of intermetallic phases. Moreover, the effect of different parameters of deviation angle, rotating velocity, linear velocity, and pin diameter on the tensile strength and Young’s modulus of the weld has been investigated. It was observed that increasing the rotating velocity from 900rpm to 1000rpm led to an improvement of about 8% in the Young modulus, while weld strength improved by 10% at a rotating velocity of 1100rpm. The optimization results showed that the Young modulus and weld strength can be improved simultaneously at a linear velocity of 30mm/min, deviation angle of $2.5^{\circ }$, rotating velocity of 1100rpm and a pin diameter of 3mm. Under the optimal conditions of the parameters, the values of tensile strength and Young’s modulus are improved up to 144MPa and 39GPa, respectively.

This study involves the preparation of hybrid bio-composites using the hand lay-up method, with epoxy resin serving as the matrix and natural fibers as the reinforcement. The primary objective was to conduct a mechanical and tribological analysis of jute–coir and banana–coir hybrid composites, as well as neat coir bio-composites. The results indicated that the jute–coir hybrid composite exhibited the lowest water absorption (7.6%) and thickness swelling (6.8%) when compared to the banana–coir and neat coir bio-composites. Moreover, the jute–coir composites demonstrated superior hardness and strength, with a higher hardness (78HRB) and tensile strength (120MPa) compared to other bio-composites. Furthermore, sliding and erosion wear tests demonstrated that the jute–coir bio-composite displayed excellent resistance to abrasion and erosion under various wear conditions. As a result, the jute–coir composite, with its reduced thickness swelling and water absorption and favorable mechanical and tribological properties, holds potential for application in diverse areas such as railway coach interiors, aircraft industries for interior components, as well as everyday items like plates and spoons.

In order to study the mechanism of decreasing tensile strength and elongation of Austempered Ductile Cast Iron (ADI) in the wet condition, various tension tests and impact tests were carried out. Three point bending fatigue tests were carried out on ADI and annealed 0.55% carbon steel to clarify the influence of water on fatigue strength. The main conclusions are as follow. Embrittlement by water begins when plastic deformation starts in a tension test. The fatigue limit of ADI in water showed a lower value than that in air. The influence of a water environment on fatigue behaviour was similar to that of annealed 0.55% carbon steel. Embrittlement such as that in a tension test was not observed in a fatigue test.

The tensile stress-strain curves of iron and a variety of steels, covering a wide range of strength level, over a wide strain rate range on the order of 10⁻³ ~ 10³s⁻¹, were obtained systematically by using the Sensing Block Type High Speed Material Testing System (SBTS, Saginomiya). Through intensive analysis of these results, the strain rate sensitivity of the flow stress for the large strain region, including the viscous term at high strain rates, the true fracture strength and the true fracture strain were cleared for the material group of the ferrous metals. These systematical data may be useful to develop a practical constitutive model for computer codes, including a fracture criterion for simulations of the dynamic behavior in crash worthiness studies and of work-pieces subjected to dynamic plastic working for a wide strain rate range.

With an aim of obtaining aluminum P/M materials strengthened by dispersion of transition metal compounds and solid solution of Mg, Al-2mass%Co and Al-5mass%Co alloys with varied Mg additions of 0, 1 and 5 mass% were prepared by rapid solidification techniques. Rapidly solidified flakes were produced by argon gas atomization and subsequent splat quenching on a water-cooled copper roll. The flakes were consolidated to the P/M (Powder metallurgy process is named as P/M) materials by hot extrusion after vacuum degassing. Cast ingots of these alloys were also hot-extruded under the same conditions to the I/M (Ingot metallurgy process is named as I/M) reference materials. Uniform dispersion of fine intermetallic compounds (Co₂Al₉) was observed in all the as-extruded P/M materials. Added Mg was present as the solute in the P/M and I/M materials alloy even after annealing at 773K. The P/M materials containing Mg exhibited higher hardness and strength than those without Mg at room temperature. Tensile strength increased with increasing amount of Mg in the I/M materials at elevated temperatures. However, strength of the P/M materials decreased with addition of Mg at 573K and 673K. According to the steady state creep rate and creep rapture time, the creep resistance of the P/M materials containing Mg was clearly inferior to that of Mg-free alloys. Thus the positive effects of Mg additions on mechanical properties of the P/M materials of Al-Co-Mg alloys disappeared at high temperature.

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 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.

According to an experimental dataset under different process parameters, support vector regression (SVR) combined with particle swarm optimization (PSO) for its parameter optimization was employed to establish a mathematical model for prediction of the tensile strength of poly (lactic acid) (PLA)/graphene nanocomposites. Four variables, while graphene loading, temperature, time and speed, were employed as input variables, while tensile strength acted as output variable. Using leave-one-out cross validation test of 30 samples, the maximum absolute percentage error does not exceed 1.5%, the mean absolute percentage error (MAPE) is only 0.295% and the correlation coefficient $(R^2)$ is as high as 0.99. Compared with the results of response surface methodology (RSM) model, it is shown that the estimated errors by SVR are smaller than those achieved by RSM. It revealed that the generalization ability of SVR is superior to that of RSM model. Meanwhile, multifactor analysis is adopted for investigation on significances of each experimental factor and their influences on the tensile strength of PLA/graphene nanocomposites. This study suggests that the SVR model can provide important theoretical and practical guide to design the experiment, and control the intensity of the tensile strength of PLA/graphene nanocomposites via rational process parameters.

Two dissimilar Al alloys, 5083-H111 and 6005A-T6, were joined by hybrid laser–MIG welding method. Mechanical properties of the welded joint were investigated and compared. The results show that the tensile strength of the dissimilar joint is 219.8 MPa, 11.7% higher than that of 6005A-T5 joint. After statistical analysis of the fatigue data, the $P$–$S$–$N$ curves of the dissimilar joint were obtained. The mean fatigue strength at $N_f=10^7$ of the dissimilar joint is 112.5 MPa. The fatigue strength at $N_f=10^7$ of the dissimilar joint for a given 10% probability of failure, at a confidence level of 95%, is 101.4 MPa. The fatigue strength at $N_f=10^7$ of the dissimilar joint is almost same as that of the 6005A-T6 joint. In welded structure designing, different $P$–$S$–$N$ curves should be chosen according to the different service conditions and reliability requirements.

In this paper, welded joints of four types of A7N01S-T5 aluminum alloy with different chemical compositions were investigated. The welding process was under 70% environmental humidity conditions at 10${}^{\circ }$C with single-pulse GMAW welding technology. The strength and fracture toughness of the four types of samples were tested, and the microstructures were investigated by micro-X-ray fluorescence (SR-LXRF) technology and backscattered electron diffraction (EBSD) technology. The results showed that the #2 alloy that is composed of Zn: 4.59 wt.%, Mg: 1.56 wt.% Mn: 0.22 wt.%, Cr: 0.14 wt.%, Zr: 0.01 wt.% and Ti: 0.027 wt.% had the best combination of tensile strength and elongation, with the values of 302.35 MPa and 3.74%, respectively. The better result for the combination of the strength and elongation was mainly determined by the volume fraction and size. The fine grain size and compositions played important roles to obtain high fracture toughness.

Aluminum alloy 6061 is widely used for space development since the advent of space era irradiated with protons using cyclotron. In the condition of confined 5-mm thick wall, protons of 5 MeV, the case of low energy showed larger damage in the structure of aluminum alloy than those of 25.4 MeV, the case of high energy. Protons of 5 MeV stopped and transferred all kinetic energy into the 5-mm thick wall, on the other hand, protons of 25.4 MeV were penetrating and a few energy transferred. Elastic modulus reduced, but elongation was increased, finally tensile strength obviously showed that longer duration of exposure yielded weaker strength of material.

Attention has been focused on the fatigue problem for compacted graphite iron, when detonation pressure and temperature becomes higher and higher in combustion chamber for a long time. The compacted graphite iron plays an important role in the cylinder head of diesel industry for its good combination of thermal and mechanical properties. The damage mechanisms of compacted graphite iron under fatigue loading are observed in this study by scanning electron microscope (SEM) and in situ technique at elevated temperatures. The results show that tensile strength of compacted graphite iron decreases slightly at first, then decreases dramatically with the increasing temperature, which is a common phenomenon, even of various metallic materials. For the compacted graphite iron, these two stages are mainly controlled by different transformation mechanisms: the former mechanism, slip band stage, is affected by the inhibition of dislocation movement including strain strengthening, dynamic strain aging and precipitation hardening; and the latter, boundary sliding stage, is controlled by the vacancy diffusion. The newly proposed mechanisms can provide a new clue for the optimization of cast iron design. These damage mechanisms lay the foundation for the application of the crack technology.

12Cr10Co3W2MoNiVNbNB (Co3W2) is a new type of martensitic heat-resistant steel, which is mainly used in high-temperature dynamic, static blades, high-temperature bolts and other components of ultra-supercritical steam turbines. The Co3W2 steel was joined by vacuum electron beam welding, and the microstructures of the joints were analyzed. The hardness, tensile strength and impact toughness of the joints were investigated. The results show that the joints mainly consist of weld metal, fusion-line, heat-affected zone (HAZ) and base metal, the microstructure of the weld metal is a coarse martensite. The hardness of the weld metal is about 326 HV higher than that of the base metal, and the tensile strength of the joints is 939 MPa, which can reach 98.63% of base metal. The impact absorbed energy of weld metal is such that the weakest part of the welded joints during the impact process is about 18.5 J.

In this study, we investigated the effects of nanoclay additives on the electrical and mechanical properties of diglycidyl ether of bisphenol A (DGEBA) epoxy resin. Epoxy-clay nanocomposites were synthesized using organically modified two montmorillonite clays (MMT) with different interlamellar spacing (31.5 Å and 18.5 Å). The electrical and mechanical properties of epoxy-clay nanocopomosites were measured with variation of the amount and type of clay. The nanocomposites were found to be homogenous materials although the nanocomposites still have clay aggregates with increasing nanoclay contents. The dielectric constant showed between 3.2 ~ 3.5 and the dielectric loss showed between 3.2 ~ 5.7% in all nanocoposites. The dielectric strength and tensile strength of the 5 wt% Cloisite 15A added epoxy-oclay nanocomposite were 23.9 kV/mm and 86.7 MPa, respectively.

Laser welding has the benefit of hardly causing welding deformation as it requires less heat input than existing welding methods. The heat input is determined by the laser output and welding speed, and the penetration depth, bead width, joining length, and bead shape are varied depending on these two welding parameters. In this study, bead and lap welding were performed on a thin pure titanium plate with a thickness of 0.5 mm using a disk laser with a maximum output of 3.3 kW. Weldability was evaluated by observing the penetration depth, bead width, joining length, and bead shape for different laser outputs and welding speeds. Results show that a weld zone with excellent joining length can be obtained for an output of 1.1 kW and speed of 2.5 m/min, as well as for an output of 1.3 kW and speed of 3.5 m/min in lap welding. Tensile-shear test was conducted with the specimens under these two conditions to investigate their mechanical characteristics.

We study experimentally the influence of mass fraction of L-20 hardener cold cure on mechanical properties of epoxy diane resin ED-20. We measure the hardness, tensile strength, bending strength and impact strength of resin at different values of the hardener mass fraction. It is found that the ratio hardener mass fraction of 1:0.9 leads to the highest values of the hardness, tensile strength, compressive strength and bending strength. The impact viscosity is maximum at the ratio hardener mass fraction of 1:0.8. The optimal ratio of a non-toxic safe hardener to the resin is derived based on obtained mechanical characteristics.

Ultrasonication is a simple way to cut carbon nanotubes in suspension. The length of fragmented carbon nanotubes is made shorter by iterating ultrasonication but approaches a critical aspect ratio. The critical aspect ratio is determined by the tensile strength of the carbon nanotube, the viscosity of the solvent, and physical properties of the cavitation bubbles produced by ultrasonication. Thus, it is possible to evaluate the tensile strength of carbon nanotubes from the critical aspect ratio. In this study, the tensile strengths of multi-walled carbon nanotubes with different diameters were evaluated using sonication-induced fragmentation. The results confirmed the strong dependency of tensile strength on diameter.

Because particles that accumulate without movement can lead to a deposition gradient, the formation of a stable suspension is essential for the electrophoretic dispersion (EPD) process. The hydrophobic properties of Halloysite nanotubes (HNTs) were easily dispersed in many nonpolar polymers without further deformation steps. However, the uniform dispersion of HNTs in aqueous solutions is a pre-EPD process task. The zeta potential controls the main parameters of EPD processes, such as the density of deposits, particle orientation and velocity, and repulsive interactions between particles, which determine the stability of the suspension. In this study, the solution stability range for the addition of nanoparticles was measured and the optimal dispersion range was determined. In addition, an HNT-reinforced composite material was created by determining the optimal dispersion stability range of HNT, and the impact strength and fracture mechanism of the interface were analyzed. The solution stability and dispersion were the best between pH 6.6 and 6.8, and the highest impact strength was confirmed at 0.7 wt%. The HNT confirmed the interfacial dispersion of the EPD-fibers using scanning electron microscopy and dispersive X-ray spectroscopy (SEM-EDS).

A theoretical study is made to derive an energy distribution equation for the size reduction process from the fractal model for the particle comminution. Fractal model is employed as a valid measure of the self-similar size distribution of comminution daughter products. The tensile strength of particles varies with particle size in the manner of a power function law. The energy consumption for comminuting single particle is found to be proportional to the 5(D−3)/3rd order of the particle size, $D$ being the fractal dimension of particle comminution daughter. The Weibull statistics is applied to describe the relationship between the breakage probability and specific energy of particle comminution. A simple equation is derived for the breakage probability of particles in view of the dependence of fracture energy on particle size. The calculated exponents and Weibull coefficients are generally in conformity with published data for fracture of particles.