Journal of Mechanics of Materials and Structures最新文献

We investigate differences in mechanical properties between anatomical regions and bearing surfaces of cortical bone at the microscale.

Eight samples were prepared from fresh femoral bones, and then loaded onto the four sides of the anatomical region, including the front, back, inside, and outside, as well as the axial and radial directions. Nanoindentation testing was performed on each sample using six indentations to acquire load-depth curves. The curves were then analyzed to determine the elastic modulus and hardness of the materials. Statistical analysis was subsequently conducted to assess the data distribution and variability. Finite element simulation may have been utilized to establish a more comprehensive mechanical behavior model.

The mechanical properties of cortical bone varied significantly across various anatomical regions and bearing surfaces, the elastic modulus and hardness of the anterior and medial sides were significantly greater compared with those of the posterior and lateral sides. The elastic modulus in the axial direction was significantly higher relative to that in the radial direction by 21.94% $(p<!--FUNCTION\; APPLICATION-->�<0.001)$. The hardness increased by 13.3% $(p<!--FUNCTION\; APPLICATION-->�=0.03)$. The elastic modulus and hardness of cortical bone increased in the same direction, showing a strong positive correlation (${R<!--FUNCTION\; APPLICATION-->}^2�=0.817$, $p<!--FUNCTION\; APPLICATION-->�<0.001$). Under the same conditions, the stresses in the axial direction of the cortical bone exceeds those in the radial direction.

A frictional receding contact problem of a functionally graded (FG) orthotropic layer / homogeneous orthotropic interlayer / homogeneous isotropic half plane system is considered. The FG layer is loaded by a rigid cylindrical punch with normal and frictional forces. While the lower layer and half plane fully bonded to each other, receding contact occurs between the upper and lower layers. It is assumed that the elastic stiffness constants for the FG layer vary exponentially in the depth direction and the Poisson’s ratios of the system are constant. The problem is converted into a system of Cauchy type singular integral equations in which the unknowns are the contact stresses on the contact areas between the punch and the FG layer, and between the FG layer and the homogeneous layer. The Gauss–Jacobi quadrature is used to discretize and collocate the singular integral equations leading to a system of algebraic equations about unknowns. Thus, the effects of some parameters such as the friction coefficient, inhomogeneity parameter, indentation load, punch radius, thickness of the upper layer on the contact areas, and the contact stresses, are presented by the results of parametric analysis.

Low heat input, less spatter and low deformation after welding are some of the advantages of joining titanium alloys using CMT welding. However, few systematic studies about the effects of welding parameters on joint formation and microstructure characteristics have been conducted. In this paper, a numerical model for CMT based on time interval loading and double ellipsoid volume heat flow distribution is established by using APDL language in ANSYS software. The effects of wire feed speed and welding speed on the temperature field, stress field and deformation cloud distribution characteristics of CMT welding for TC4 titanium alloy are studied. The numerical simulation results in a high degree of coincidence with the experimental weld, with an average error of no more than 7%. At the same time, the influence of wire feed speed and welding speed on the surface formation and microstructure of the weld is experimentally studied in this paper. The results of numerical simulation show that with the increase of wire feed speed, the area of high temperature zone of the joint enlarges. The peak temperature at the arc closing position changes from 2858 ${}^{\circ }$C to 4182 ${}^{\circ }$C. As the welding speed increases, the area of high temperature zone of the joint shrinks. The peak temperature at the arc closing position decreases from 4722 ${}^{\circ }$C to 2133 ${}^{\circ }$C. When the wire feed speed is 5.5 m/min and the welding speed is 0.45 m/min, the maximum von Mises residual stress on the upper surface is relatively small, 730 MPa, and the maximum deformation is relatively small, 0.869 mm. The experiment results show that with the increase of the wire feed speed, the melt width on the front side gradually increases and the formation of the back side gradually changes from discontinuous to continuous and uniform. The average grain size in the weld increases from 10.0 $\mu$m to 16.7 $\mu$m. With the increase of welding speed, the melt width on the front side gradually decreases and the formation of the back side gradually changes from continuous and uniform to discontinuous. The average grain size in the weld decreases from 14.3 $\mu$m to 9.1 $\mu$m.

The failure of unreinforced masonry structures (e.g., a collapse) because of their vulnerability to earthquake action poses an actual threat to human life. Researchers have investigated many mortar-free interlocking techniques. But the mass of interlocking blocks is a point of concern. The interlocking plastic-blocks are lighter in weight, possibly causing a lesser lateral force during the strong ground motions. However, the dynamic response of such structures is unknown. Therefore, the objective of this research is to examine the dynamic behavior of the scaled down model of the interlocking plastic-block wall having window in comparison with a model of an unreinforced masonry wall with the same elevation dimensions. Two dynamic tests, i.e., snapback and harmonic loading, are conducted in the out-of-plane direction. From the snapback test, the fundamental dynamic characteristics i.e., fundamental frequencies and damping ratios are experimentally determined. For learnt frequencies from snapback tests, three harmonic loadings are applied one by one using a locally developed unidirectional shake table. Acceleration time and displacement time histories are used to study the behavior of walls. Base shear displacement curves are used to determine energy absorption. Empirical equations are established by taking into consideration the input loading parameters, wall height, and geometry of interlocking blocks. It is found that the interlocking plastic-block wall is more resistant to unidirectional lateral loading when compared with a masonry wall.

With the wide application of functionally graded carbon nanotube reinforced composite (FG-CNTRC) structure in engineering, vibration and noise are inevitable in the complex working environment. This paper investigated the acoustic response and wave propagation characteristics of FG-CNTRC plates. Based on the third-order shear deformation theory, the dynamic equation of FG-CNTRC plate was derived using Hamilton’s principle. The acoustic response characteristics of FG-CNTRC plate under the concentrated harmonic excitation were solved and verified. By using the displacement function of wave propagation in an infinite plate, the dispersion characteristic equation of FG-CNTRC plate was obtained, and its dispersion curve, phase velocity and group velocity were solved. Then, the effects of parameter changes on the acoustic response and wave propagation in the FG-CNTRC plate were analyzed and discussed. This research provides a theoretical reference for the optimization design of FG-CNTRC structures.

In this article, molecular dynamics simulation method was used to establish a high entropy alloy atomic model, and different impact velocities were applied to study the impact induced high entropy alloy phase transformation and dislocation motion mechanism. It creatively reveals the evolution mechanism of thermal mechanical coupling response of FeCoCrCuNi high entropy alloy under impact loading. The results show that when the impact speed is higher than 1400 m/s, the temperature rise breaks through 5000 K under the impact, and the high entropy alloy particles become amorphous. When the impact speed reaches 1000 m/s, the atomic motion speed of Ni and Cu atoms is slightly increased compared to other elements, and the face-centered cubic (FCC) phase is largely transformed into hexagonal close-packed (HCP) phase, with the dislocation density reaching its peak. After passing through the wavefront, twinning is formed under the action of cross slip and dislocation reaction, which prevents further expansion of dislocations and forms a dislocation hollow area, enhancing the strength of localized materials.

In this paper, the load-carrying capacity of an infinite elastic-perfectly plastic plate containing five collinear straight cracks with coalesced yield zones was studied using a modified Dugdale model. Important parts of this study are the coalescence of yield zones developed at the internal tips of closely located outer pairs of cracks and the influence of quadratically varying yield stress distribution on the load-bearing capacity and crack-tip opening displacement. Traditional concepts of Muskhelishvili’s complex variable method have been used to obtain analytical expressions for complex potential functions, stress intensity factors (SIFs), yield zone length, and crack-tip opening displacements (CTODs). Numerical results are obtained and shown graphically for yield zone length, applied load ratio, and CTODs. A good agreement of the results is seen with previously published work as limiting cases.

Due to the high theoretical capacity and environmental benignity, the tin (Sn) anode is one of the most promising candidates for applications as an electrode. Using an image-based finite element approach, we rebuilt the Sn active phase and evaluated the distribution of Li-ion concentration and evolution of stress. To account for the large deformation of the Sn electrode during the charge/discharge process, we proposed a theoretical framework based on viscoplasticity theory to study the chemomechanical coupling behavior of the Sn anode. First, we applied finite deformation theory to investigate the proposal that viscoplasticity induced the reduction in von Mises stress. Then, considering the stress-dependent diffusion in Li-Sn systems, the effects of microstructure on the stress evolution, local electric potential, and cycle performance were elucidated. Our results revealed that the microstructure significantly influenced the stress field and distribution of electric potential. Additionally, our results showed that concentration distributions result in a sharp gradient and that the von Mises stress varied significantly at the chosen concave or convex sites of the surface. Then, we proposed the effects of the number of cycles on the plastic stress and the stress-biased voltage. As a result, the predicted behavior of real microstructure has the potential to be utilized in the design of electrodes with tunable microstructure.

As a typical nonsmooth strong coupling dynamic problem, the vibrational analysis on the plate subjected to the oblique impact requires us to develop the effective method that can be used to deal with the nonsmooth strong coupling problem well. Focusing on the local dynamic behaviors of the impact system, the generalized multisymplectic method is employed to reproduce the dynamic response of the finite plate on the elastic foundation subjected to an oblique impact in this paper. Firstly, the first-order approximate symmetric form of the dynamic equation describing the vibration of the finite plate on the elastic foundation subjected to an oblique impact is deduced based on the multisymplectic theory. Then, a generalized multisymplectic scheme equivalent to the Preissmann scheme for the first-order approximate symmetric form is constructed. The validity as well as the high precision of the generalized multisymplectic scheme are verified by the finite element method and the approximate theoretical solution in the numerical simulations finally. From the numerical results, the effects of the angle parameters for the oblique impact on the maximum transverse displacement of the plate are discussed in detail. The main contribution of this work is proposing a structure-preserving method to investigate the nonsmooth strong coupling dynamic problem effectively.

All-metal sandwich panels of auxetic honeycomb are usually ultralight and robust but have poor vibration damping. The in-plane auxetic honeycomb sandwich panels (AHSPs) with polyurea-metal laminate (PML) were presented, and its vibration and damping characteristics were studied. The damping characteristic analysis model of the auxetic honeycomb sandwich structure of the PML panel was created by ABAQUS and the model was verified. The frequency/time response curve, natural frequency, mode shapes, and damping loss factor were simulated by the finite element (FE) method, which was then compared with the sandwich plate without a polyurea layer. To investigate potential enhancement processes and examine vibration-damping characteristics, a finite element-modal strain energy (FE-MSE) integrated approach was put forward, taking into account the natural frequency and damping behavior of polyurea. The damping of the PML panel significantly increased due to the viscoelastic energy consumption of the polyurea layer. By reasonably adjusting the thickness and distribution of the polyurea layer, the passive damping ability of sandwich panels can be further enhanced. The frequency and damping loss factor of the AHSPs were able to be successfully improved by raising the thickness of the polyurea layer. The symmetric PML-A laminate was better than the asymmetric structure in vibration reduction, and the damping loss factor can grow from 29% to 40%, with a thickness ratio of $\frac{3}{3}$.