Narrow Results

Power series method is used to analyze the distribution of stresses of the transversely isotropic cylinder under arbitrary axisymmetrical normal load. The stress function and normal load are expanded as the form of Fourier series. Unknown parameters in equations are determined using boundary conditions and final solutions of stress and displacement are obtained accordingly. The analysis of stresses obtained from different material parameters shows that the axial stress is significantly affected by Young's modulus and the circumference stress is sensitive to the variation of Poisson's ratio.

Mechanical performance parameters such as the fatigue strength, tensile strength, ductility and Young's modulus of newly developed Ti-29Nb-13Ta-4.6Zr, referred to as TNTZ, can be improved considerably by microstructural control via thermomechanical processing. Thermomechanical processing including severe cold wire drawing can generate functionalities such as super elasticity in TNTZ. The abovementioned improvement in the mechanical performance and functionality of TNTZ is associated with its nanosize structure. The cytotoxicity of TNTZ is very low and equivalent to that of pure titanium. It is expected that TNTZ will be used as a structural biomaterial.

The nanoindentation technique was used to measure the hardness and Young's modulus of semiconductor and metal thin films on a Si(100) substrate under cyclic loading. The results showed that in all instances and at a constant cyclic load that the loading curves overlapped the previous unloading curve and had a small displacement after each cyclic nanoindentation. It was observed that the plastic energies of metal materials from the first loading–unloading cycle were much larger than that observed in semiconductor materials. Furthermore, the hardness and Young's modulus of the thin films decreased when the number of cyclic nanoindentations was increased. The effect of the cyclic loading on the hardness and Young's modulus of semiconductor material was much larger than that of the metal material. Young's modulus, the hardness and the contact stiffness of thin films conform to the relationship that Young's modulus was proportional to the contact stiffness and the square root of the thin film's hardness.

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.

Molecular dynamics (MD) simulations are employed to study the elastic properties of gallium nitride (GaN) nanosheets. Young’s and bulk moduli of GaN nanosheets with different side lengths and height/width ratio are obtained. Besides, the configuration of the nanosheet at different strains is represented until the fracture initiation and final fracture are observed. It is seen that the zigzag nanosheets have larger elastic moduli than armchair ones with the same sizes. Moreover, increasing the length size of the nanosheets results in decreasing Young’s modulus. Bulk moduli of GaN nanosheets are also obtained by applying biaxial loading on all edges. It is seen that under the biaxial tensile force, the fracture is initiated at the nanosheet corners and is continued toward the nanosheet center. A nonlinear relation between the bulk modulus and nanosheet size is observed.

In this paper, we used the first-principles method to investigate the structural, electronic, mechanical and thermodynamic parameters of the ternary $\beta$-Ti–15Nb–xSi alloys with $x=0.6,0.8,1,1.2,1.4,1.6$wt.%. We have carried out theoretical computations inside the density functional theory (DFT) utilizing the generalized gradient approximation (GGA) with the Perdew–Burke–Ernzerhof (PBE) model. The random distribution of Nb atoms in the alloy was described by using both virtual crystal approximation (VCA), special quasirandom structure (SQS) and the coherent potential approximation (CPA) techniques, in combination with first-principles plane-wave pseudopotential (PW-PP) and exact muffin-tin orbital (EMTO) methods. We determined the elastic constants as well as the bulk, shear, Young’s modulus and Poisson’s ratio. Our structural results are in good agreement with the available experimental and theoretical results for the pure structure of the titanium. In addition, we have estimated the band structure and the density of state (DOS) for the electronic computations. Our findings demonstrate that all of the compounds are metallic, stable and meet the requirements for stability. Young’s modulus of Ti–15Nb–0.6Si and Ti–15Nb–1.6Si is 86.5GPa and 15.11GPa, respectively, which are similar to Young’s moduli of human bone (10–30GPa). All calculated parameters of the alloys decreased with increasing of Si concentration except for Poisson’s ratio, anisotropy and B/G ratio. Furthermore, all of the materials investigated showed ductile nature, and Young’s modulus values are needed for further applications. Excitations from the quasi-harmonic Debye approximation’s vibrational part were applied to the 0K free energy calculated via ab-initio calculations. The influence of temperatures up to 800 K on phase stability was investigated. These findings can be utilized to help designers create alternative low-modulus alloys for biomedical applications.

Stainless steel (SS) is widely used in many fields including aeronautics, automobiles, marine and mechanical industries due to its outstanding feature such as good corrosion resistance and hardness. However, changes in material properties under stress, particularly changes in Young’s modulus, result in the formation of cracks, a reduction in load-bearing capacity, and fatigue damage. So, the structural integrity needs to be evaluated based on a precise measurement of mechanical properties. In this study, Stainless Steel 304 (SS-304) is used as the base material and various tensile stresses are applied ranging from 0MPa to 100MPa with increment of 10MPa in each step. Nondestructive Laser Ultrasound Technique (LUT) has been used to characterize the elastic modulus under various tensile stresses. An inverse program was developed based on the Particle Swarm Optimization (PSO) algorithms to determine material properties. Nonlinear Gauss fitting method was proposed and established the fitting equation and nonlinear curve for Young’s modulus and residual stress. The outcome of this research shows that when tensile stress is applied, the mechanical properties decrease by shifting the dispersion curve and also it is evident that the dispersion curves move toward the high-frequency-thickness while increasing the tensile stress. When the tensile stress was increased from 0MPa to 100MPa, the value of Young’s modulus decreased from 201.7GPa to 193.5GPa. Especially, the predominant changes were observed during 30–100MPa. This observation displays the bonding strength and binding energy between the atomics. Further, the proposed nonlinear Gauss fitting substantiated the experimental values and confirmed that the thickness accuracy is close to the inversion values, with an average difference of 4.32%. This research suggests a potential nondestructive method to determine the residual stress of a material by calculating the changes in the elastic modulus.

It is natural to treat the monolayer crystalline film as the surface fixed by the positions of atoms. However, this type surface is not well-suited to the monolayer crystalline film. It has been discovered that the mechanical properties of a monolayer crystalline film can be described exquisitely by its inscribed surface. Depending on this inscribed surface of armchair carbon nanotubes, the present study shows the reason why CNTs cannot be simply considered as a thin shell with constant thickness. Application of the present model to armchair CNTs predicts that the ranges of Young's modulus and effective thickness are respectively from 2.407 to 3.209 TPa and from 0.082 to 0.073 nm, which are in good agreement with previous theoretical studies and experimental observations.

This investigation described the development of a technique to produce Au–Co nanostructured composite coatings with improved hardness. Pulse power has been used with the traditional Au electroplating solution to synthesize multilayer nanocomposite coatings. The phase structure was analyzed by X-ray diffraction. Mechanical properties were investigated using nanoindentation. The results indicate that the hardness was increased to 3.15 ± 0.05 GPa, compared to 2.70 ± 0.07 GPa of that produced by the direct current Au coatings. The hardening mechanisms have also been discussed.

This paper studies the mechanical properties of polyethylene (PE)–Single-walled carbon nanotube (SWCNT) complexes by using density functional theory (DFT). At the PBE/SVP level, the Young’s modulus of the complexes is obtained as a function of PE content. It is established that, with increasing number of PE chains attached to the SWCNTs, the Young’s modulus monotonically decreases. The density of states (DOS) results show that no orbital hybridization exists between the PE chains and nanotubes. The results of this work are of importance for the design of composite materials employing SWCNTs.

The impact of shape, size and temperature on elastic properties of nanomaterials is studied in this work. We have extended the melting temperature expression for nanostructures formulated by Guisbiers et al. and obtained the expression of elastic moduli and thermal expansivity for nanomaterials. An isobaric Tait equation of state is combined with Guisbiers model and the model so obtained is applied to analyze the shape, size and temperature effect on Young’s modulus and thermal expansivity in nanomaterials. The present computed results are compared with the simulated results and available experimental data. The Young’s modulus is observed to decrease as particle size is reduced while thermal expansivity increases with decrease in the size of nanomaterial. The Young’s modulus shows decrease with increase in temperature and decrement is observed maximum in spherical nanomaterials and minimum in nanofilms (NFs). Rate at which modulus is decreasing is found to increase as particle size is reduced. Good consistency of present predicted results with the available theoretical and experimental data is observed. The present calculated results are thus found consistent with the general trend of variation.

Based on the semi-continuum model, the effect of temperature on Young’s modulus in the presence of oxide layer in silicon nano-films was studied theoretically by using the anharmonic Keating deformation potential, and the effect of oxide layer on Young’s modulus was also studied. The results show that Young’s modulus of the nano-film is inversely proportional to its temperature, which decreases with the increase of temperature. And with the number of oxide layer increasing, Young’s modulus of silicon nano-film increases. At the same thickness and layer numbers, Young’s modulus of the films with oxide layer is larger than that of pure silicon nano-films. The existence of oxide layer leads to the increase of Young’s modulus of the silicon nano-film.

Temperature dependence of Young’s modulus of Ag microwhiskers was determined by a laser Doppler vibrometer. The Ag whiskers with diameters in sub-microns were synthesized by the use of physical vapor deposition (PVD). They have a five-fold twinned structure grown along the [1 1 0] direction. The temperature coefficient of Young’s modulus was measured to be $485.0\pm 16.8$ ppm/K in the range of 300 K to 650 K. The measured values are very close to the reported values of $410\sim 449$ ppm/K for bulk Ag single crystals. This finding can benefit the design of Ag-based micro/nano-electromechanical systems or micro/nano-interconnectors operated at elevated or lowered temperatures.

As the 1988 radiocarbon dating of the Turin Shroud (TS) was debatable also from a statistical point of view, new dating methods have been proposed. This paper presents the result of an improved mechanical dating. A recent cyclic-load machine has been improved to better fix fibers under test by using a special support designed for the purpose. The mechanical behavior of linen fibers of three different ages are measured and compared discussing these results in reference to the complex structure of aged linen fibers; the three samples are a linen fiber from an Egyptian mummy of 27${}^{\mathrm{\text{th}}}$ Century B.C.; a linen fiber coming from the TS, and a recent linen fiber. This machine allowed to confirm the previous results regarding the TS mechanical dating, showing that these results are again compatible with the First Century A.D., the period in which Jesus Christ lived in Palestine. The improved machine also showed that the complex nonlinear behavior of the fibers is also due to the packing of the Secondary Cell Wall of the linen fibers, mostly composed of micro fibrils, that produces a memory-effect. The stiffening of the linen fibers with the loading increasing is a property detected for all the tested fibers that must not be forgotten also in the construction of flax fibers based composites.

Size-dependent elastic properties of Ni nanofilms are investigated by molecular dynamics (MD) simulations with embedded atom method (EAM). The surface effects are considered by calculating the surface relaxation, surface energy, and surface stress. The Young's modulus and yield stress are obtained as functions of thickness and crystallographic orientation. It is shown that the surface relaxation has important effects on the the elastic properties at nanoscale. When the surface relaxation is outward, the Young's modulus decreases with the film thickness decreasing, and vice versa. The results also show that the yield stresses of the films increase with the films becoming thinner. With the thickness of the nanofilms decreasing, the surface effects on the elastic properties become dominant.

The Young's moduli of electrodeposited Ni with different dimensions were measured carefully in this paper. The dimensions of tensile specimens were 200, 35, or 5 μm thick and 2400, 200 or 50 μm wide. These specimens were measured with three different approaches. The measured Young's moduli of Ni decrease from 122.1 ± 4.3 to 92 ± 5.2 GPa when the thickness changes from 200 to 5 μm and width changes from 2400 to 50 μm.

Nanoporous materials and structures have attracted widespread attention due to their excellent mechanical properties. Based on the surface elasticity, the effective Young’s moduli are derived for four typical nanoporous structures with periodic unit cells. When the cross-sectional size reduces to nanoscale, the effective Young’s modulus is revealed to be strongly size-dependent. Both the effects of residual surface stress and effective-surface Young’s modulus are examined. The results indicate that negative effective Young’s modulus can be achieved when the residual surface stress is less than zero. The influences of the cross-sectional shape on the relationship between the overall deformation and applied loads are examined. The relative density also plays an important role to the mechanical characteristics not only at macroscales, but also at nanoscales.

In this work, an attempt has been made to correlate the dielectric permittivity of polyacrylamide based tissue mimicking phantoms with their mechanical properties such as breaking stress, breaking strain and Young's modulus. The tissue mimicking phantoms of various concentrations were prepared as per the standard protocol and their permittivity was measured using a precision impedance analyzer. The mechanical properties of the phantoms were measured by conducting tensile tests using a Universal Testing Machine. The measured mechanical properties were correlated with the dielectric permittivity by performing statistical analysis. Results demonstrate that the percentage variation in the mechanical properties correlate well with the percentage variation in the permittivity of the tissue mimicking phantoms. Further, it appears that the changes in the mechanical properties of the phantoms can be estimated by quantifying the changes in their dielectric permittivity. In this paper, the objectives of the study, methodology and significant observations are discussed in detail.

The objective of this study is to explore the feasibility of a compression test for measuring mechanical properties of intact eye lenses using novel parallel plate compression equipment to compare the accuracy of implementing a classical Hertzian model and a newly proposed adjusted Hertzian model to calculate Young’s modulus from compression test results using finite element (FE) analysis. Parallel-plate compression tests were performed on porcine lenses. An axisymmetric FE model was developed to simulate the experimental process to evaluate the accuracy of using the classical Hertzian theory of contact mechanics as well as a newly proposed adjusted Hertzian theory model for calculating the equivalent Young’s modulus. By fitting the force-displacement relation obtained from FE simulations to both the classical and adjusted Hertzian theory model and comparing the calculated modulus to the input modulus of the FE model, the results demonstrated that the classical Hertzian theory model overestimated the Young’s modulus with a proportional error of over 10%. The adjusted Hertzian theory model produced results that are closer to original input values with error ratios all lower than 1.29%. Measurements of three porcine lenses from the parallel plate compression experiments were analyzed with resulting values of Young’s modulus of between 3.2kPa and 4.3kPa calculated. This study demonstrates that the adjusted Hertzian theory of contact mechanics can be applied in conjunction with the parallel-plate compression system to investigate the overall mechanical behavior of intact lenses.

Bone remodeling is a physiological phenomenon coupling resorption and formation processes that are mainly mediated by osteoclasts and osteoblasts, in response to mechanical stimuli transduced by osteocytes to biochemical signals activating the bone multicellular unit. Under normal loading conditions, bone resorption and formation are balanced by a homeostasis process. When bone is subjected to overstress, microdamaging occurs, which induces a modification of the structural integrity and microarchitecture. This has drawn significant attention to the mechanical properties of bone. In this context, the current study has been carried out with the aim of numerically investigating the impact of the mechanical properties on the remodeling process of the trabecular bone under cyclic loading, highlighting the effects of different values of the mineral density and the Young’s modulus. This was performed using a mechanobiological model, coupling mechanical and biological approaches, allowing to numerically simulate the effect of the selected parameters for a 20-year-period of cyclic loading for 2D and 3D models of a human femur head. The current work is an explorative numerical study, and the obtained results revealed the changes in the overall stiffness of the bone according to the mechanical properties.