Mechanics of Solids最新文献

Polycrystalline copper is widely used in multiple areas such as chip interconnects, nanoelectrodes, and nanoscale devices due to its unique electrical, thermal, and mechanical properties. Unlike monocrystalline materials, the presence of disordered grain boundaries and crystal orientations in polycrystalline materials significantly affects the chip formation mechanism during nanoscale machining. To investigate the influence of microstructural characteristics, such as grain size and grain boundary angle, on the chip formation process, a molecular dynamics model for polycrystalline copper was developed. The study systematically analyzed the evolution of the crystal structure, crystal orientation distribution, as well as the strain and stress during the chip formation process. The results indicated that the chips formed during the nano-cutting of polycrystalline copper are almost sawtooth-like, and the shear strain, crystallographic orientation, and crystal structure within the chip are periodically distributed. It is found that, an inclined grain boundary can effectively reduce shear strain on the machined surface, thereby improving the quality of the machined surface, and a highest surface quality can be achieved when the grain boundary angle approaches to 150°. Moreover, the results indicated that the chip was formed through two ways, namely, the extrusion and shear. The workpiece material near the tool tip was destroyed by the extrusion of the cutting tool, forming the flowing chip with amorphous atoms. On the other hand, the workpiece material near the free surface was separated by the periodically emerged shear slip bands. For these two chip formation processes, the extrusion process is not affected by grain boundary, but the shear process is dominated by the inclined angle of grain boundaries, the direction of the shear slip may be along the grain boundary or through the grain boundary.

The increasing demand for accurate modeling of heat transport in micro/nano-scale devices and ultrafast laser applications reveals the limitations of classical heat conduction theories like Fourier’s law. To address this, a novel framework for generalized thermoelasticity is proposed, incorporating a non-Fourier heat conduction law grounded in thermomass theory—where heat is modeled as the motion of an equivalent mass of phonon gas. The model also integrates a nonlocal formulation for stress and incorporates memory effects via the memory-dependent derivative (MDD), allowing for the influence of past thermal states.

The study considers a one-dimensional thermoelastic rod subjected to ramp-type thermal loading at one boundary, with the other end maintained at zero temperature. Both ends are mechanically fixed. The governing equations are solved in the Laplace domain, and numerical inversion using Zakian’s technique is applied to obtain time-space domain results. Different types of kernel functions are introduced to capture memory effects, and nonlocality is embedded in the stress field.

The results demonstrate that kernel choice, nonlocal length scale, ramp duration, and delay-time parameters significantly influence temperature, stress, and displacement distributions. Comparisons with the classical Lord–Shulman model reveal the proposed theory’s superior capability in capturing wave-like thermal and mechanical behavior, especially under conditions involving finite speed heat propagation and size-dependent effects.

Aiming at the problem of flutter and instability of supersonic panel. the nonlinear dynamic control equation of pre-stretched porous panel is established based on Von Kármán thin plate large deflection theory and first-order piston aerodynamic load model. The dynamic model incorporates pre-stretching effects in functionally graded porous panels. Considering three different pore distribution modes. The Galerkin method transforms the governing equations into nonlinear systems through chordwise integration. Stability criteria are derived via Routh-Hurwitz analysis and Hopf bifurcation theory. Closed-form solutions for critical frequency and flutter velocity are obtained. Numerical validation is performed using fourth-order Runge-Kutta integration. Results demonstrate superior performance in symmetric distribution cases: It demonstrates the best flutter resistance, followed by asymmetric and then uniform distributions. The application of merely (0.02% ) pre-stretching strain results in significant improvements in both critical flutter velocity and flutter frequency; when compared to the non-pre-stretched condition, the pre-stretched configuration delays the system critical point occurrence, effectively reducing flutter incidence. The pre-stretching-porosity coupling control methodology proposed in this study, establishes a new theoretical paradigm for panel design: prioritizing symmetric porosity distribution with optimal pre-stretching strain, can effectively suppress flutter while enhancing stability performance.

Geometric nonlinear problems are common in engineering, and it is very difficult to obtain an analytical solution. Furthermore, mesh-based numerical methods suffer from high computational complexity, low efficiency and poor accuracy in solving the geometric nonlinear problems due to mesh constraints. To address this issue, this paper presents a nonlinear Hermite interpolation meshless method (HIMM) for large deformation analysis of elastomers. This method utilizes a set of discrete nodes to represent the problem domain, avoiding mesh generation and reconstruction. Firstly, the governing equations of the geometric nonlinear problems are obtained based on the virtual displacement principle and full Lagrangian formulation. Secondly, the approximation function of the displacement field is derived using the Hermite approximation method and moving least squares method. Then, the meshless formulation is obtained, and the HIMM model for the geometric nonlinear problems is established. Finally, the influence of the scale factor, load step and node density on the accuracy of the HIMM model is analyzed, and the effectiveness of the HIMM for solving geometric nonlinear problems is verified through several examples. The numerical results show that the computational accuracy of the HIMM is 3 to 6 times higher than that of the existing element-free Galerkin method (EFGM). In addition, the HIMM reduces the computation time by approximately 50% compared to the EFGM. This work provides an effective numerical tool for geometric nonlinear problems, and also provides a reference for applying meshless methods in the engineering field.

In this paper, the first investigation of axially functionally graded porous (FGP) configuration of three-dimensional graphene foams (3D-GFs) structures is carried out and the vibration characteristics of conventional radially FGP cylindrical shells are comparatively analyzed. To begin with, predicting equivalent material properties of bi-directional FGP 3D-GFs by utilizing open cell body theory. Moreover, based on the regional decomposition method, the cylindrical shell is divided into a number of segments along the axial direction, and the appropriate artificial spring stiffness values are selected to simulate the connection conditions between each section and the boundary constraints of the shell structure in the actual working conditions. Meanwhile, the vibration characteristics of the shell under arbitrary boundary conditions are explored on the basis of the first-order shear deformation theory (FSDT) and the Gegenbauer-Ritz method. The axially FGP structures are analyzed in comparison with the radial configurations, while the influence of factors such as boundary conditions, FGP types, and geometrical parameters on the natural characteristics of the shell is discussed. The research shows that the framework of 3D-GFs, which is distributed more at the boundary ends and inner and outer surfaces of the shell, has the most reinforcement effect on the overall stiffness of the structure, and the radially FGP configuration is more competitive.

Functionally gradient materials have attracted extensive attention and research due to their remarkable resistance to thermal shock under harsh thermal conditions. In addition, the analytical model of thermoelasticity encounters pronounced limitations when applied to micro-structures. This deficiency can be ascribed to its failure to incorporate the ramifications of the spatially size-dependent effects that are intrinsically linked to heat transfer and elastic deformation. To accurately model the thermo-mechanical coupling at nanoscale, a nonlocal dual-phase-lag thermoelasticity with nonlocal elasticity effect is given in this work. In the aspect of application, the thermo-mechanical behavior of a functionally graded spherical microshell heated by a thermal-mechanical loading is studied. Governing equations including the nonlocal thermal parameter, the nonlocal elasticity parameter, the power law index are derived solved by Laplace transformation. It is shown by the achieved results that the thermal deformation under ultrafast heating condition will be reduced when the influences of nonlocal effect and ceramic composition are considered.

This work examines the effects of memory and phase lags on an infinite elastic circular plate with finite width subjected to axisymmetric thermal and mechanical loadings, utilizing the hyperbolic two-temperature three-phase lag model of generalized thermoelasticity with temperature-dependent material properties. For the two-dimensional problem under consideration, governing equations are determined. At uniform temperature, the plate is first thought to be unstressed and unstrained. The governing equations are reduced to a non-dimensional form and simplified using potential functions. The combined Laplace and Hankel transforms are employed to simplify the problem into ordinary differential equations. The eigenvalue approach is utilized to address the problem, and the arbitrary constants in the solution are determined by applying the loading conditions on the boundary surfaces. In the Laplace and Hankel transform domain, the temperature fields and normal stress are calculated analytically in compact form. To obtain the field quantities in the original region, a numerical inversion technique is employed.

During the major overhaul of the aircraft accessory housing, oil leakage was detected at the cover plate of the DC motor bracket. Inspection revealed that the graphite sealing assembly used for sealing had failed, with one of the rubber O-ring components showing surface indentations and adhesion to the inner wall of the graphite ring. The failure of this type of sealing assembly primarily manifests in two categories: damage to the graphite sealing ring and damage to the rubber O-ring. While the former has been extensively studied, the latter has received very little attention. In this study, three experiments were conducted on the FX-4 rubber O-ring: model theory analysis, dimensional control assembly testing, and temperature influence testing. These experiments revealed the effects of design dimensions and temperature changes on the damage to the O-ring in the graphite seal assembly.

This paper presents an energy-based approach for predicting elastoplastic fracture, formulated through the concept of a critical strain energy threshold. The method combines a newly introduced energy fracture criterion with a modified relaxation model of plasticity belonging to the structural-temporal class of theories. This combination enables the accurate description of materials exhibiting complex deformation behavior, including non-monotonic stress–strain curves and the yield point phenomenon, which are particularly relevant for metallic materials deformed at relatively low strain rates.

A key advantage of the approach lies in its compactness and physical interpretability: the model parameters are directly related to the material’s initial defect structure and remain independent of the loading history. This allows for predictive capability across different grain sizes and material states without introducing damage accumulation functions or additional fitting parameters.

The model is validated against experimental data for magnesium alloys Mg–0.3Ca (wt %) and Mg–1.0Al–1.0Ca–0.4Mn (wt %) with varying grain sizes. The predicted deformation curves (up to fracture) show good agreement with the experiments, even under conditions of developed plastic deformation. In one case, a single critical energy value proved sufficient, while in the other, a Hall–Petch-type grain size dependence was incorporated. The proposed framework shows strong potential for extension to more complex loading paths and other classes of metallic alloys.

This paper aims to establish a new dynamic model of a bolted rotor system that takes into account rubbing faults and non-uniform preload, and comprehensively studies and analyzes the effects of rubbing faults and non-uniform preload on the dynamic response of the rotor system. A dynamic model of a bolted joint rotor system is established based on the lumped mass modeling approach. The dynamic response of the rotor system is computed using the Newmark-β numerical integration method. Parametric studies investigate the effects of rubbing faults and non-uniform preload on the system’s dynamical behavior. Results demonstrate that the coupling between rubbing faults and piecewise linear stiffness characteristics exacerbates critical speed reduction while increasing vibration amplitude. Furthermore, experimental validations conducted on a bolted joint rotor system equipped with a rubbing device partially verify the numerically predicted results regarding the effects of non-uniform preload and rubbing faults on rotor dynamic characteristics. This paper draws some conclusions on the dynamics of bolted rotors based on rubbing fault and non-uniform preload by comparing numerical and experimental results, which are of reference value for the motion control and fault diagnosis of bolted rotor systems.