Mechanics of Solids最新文献

his work presents an analytical investigation of photothermal effects in a semiconducting strip containing a traction-free crack under antiplane shear deformation. A novel coupling between mechanical displacement, temperature field, and carrier density is considered under constant thermal loading at the upper boundary, extending traditional antiplane crack models. Solutions for displacement, temperature, carrier density, and shear stresses are obtained using Fourier transform techniques within the frameworks of Lord–Shulman, Green-Lindsay, and Classical Coupled Thermoelasticity theories. Numerical evaluations performed via MATLAB reveal pronounced differences among the three models, particularly in the attenuation of temperature and stress fields near the crack tip due to thermal relaxation effects. These results provide new insights into the thermomechanical behavior of semiconductor materials with defects, offering a foundation for improving the design of optoelectronic and microelectromechanical systems under combined thermal and mechanical loading.

Thermoelastic damping (TED) is an important factor in modeling and designing of micro-/nanoscale devices. The present study proposes to study thermoelastic damping in piezothermoelastic beam at nanoscale using nonlocal modified couple stress theory (NMCST) which is a combination of Eringen’s nonlocal elasticity theory and modified couple stress theory. Coupled thermoelastic equations are derived using NMCST based on Euler-Bernoulli beam theory. The complex frequency approach has been used to solve the coupled equations and thermoelastic damping has been obtained for piezothermoelastic nanobeam under simply suppoted-simply supported (SS) boundary condition. The results obtained are compared to those obtained from classical continuum and heat conduction theories. MATLAB software has been used to discuss the results graphically.

The modeling of complex geometries with cutouts in NUBRS-based isogeometric analysis usually needs a multiple-patches strategy. It is still an obstacle because of the requirement of very specialized knowledge of computer-aided design (CAD) to generate a NURBS mesh. In this paper, a cut NURBS element method is proposed for the free vibration and buckling analysis of the complex-shaped laminate Reissner-Mindlin plate. Here, three major issues including the shearing locking, the representation of the cut objects, and the localized eigenmodes must be addressed. Firstly, in order to address these issues, an artificial shear correction factor is introduced to avoid shearing locking. Secondly, a level set approach on a structured NURBS mesh is used to produce the cut NURBS element as well as describe the arbitrary and crisp interface between the cut objects and the initial simple geometry through the thresholding of the level set value. Then, a segmented density method is adopted to represent the contribution of the solid, void, and cut NURBS elements. Finally, the different density interpolation formulas for element stiffness, mass, and geometrical matrices are introduced to overcome localized eigenmodes. The numerical results show the proposed method can effectively avoid the existence of shear locking and localized eigenmodes. By comparing with the results from other methods, the proposed method is proven to obtain highly accurate numerical results and effectively reduce computational cost.

In the present study, we examine the fundamental solution and Green’s function in a semi-infinite orthotropic micropolar photothermoelastic medium based on Moore-Gibson-Thompson heat equation (MPMGT). To achieve this, we first translate the governing equations into two dimensions and execute the dimensionless quantities, and then we employ operator theory to derive the general solution for the MPMGT model. The fundamental solution and Green’s function for a steady point heat source on the surface and in the interior of a semi-infinite medium of the assumed model have been computed from the general solution using newly introduced harmonic functions. To investigate the micropolarity effect, displacement, stress, temperature, carrier density distribution, micro rotation and couple stress are computed numerically and presented as graphs. Specific cases are inferred from the current investigation and compared with the previously established results. The obtained results have applications in the material and engineering sciences, as well as in the different semiconductor elements during the coupled photothermoelastic impact.

Concentric cable-driven manipulators (CCDMs) are dexterous enough to be widely used in confined space. While how to adaptively plan a smooth end path for CCDMs has become a key issue. In this paper, an Adaptive Smoothing Rapidly exploring Random Trees (AS-RRT) method is proposed for path planning of CCDMs. Firstly, the binocular vision is used to detect the target node and obstacles to further establish complete coordinates of oral environment. Secondly, the sampling convergence optimization strategy and the target gravitational bias strategy are detailed to adaptively optimize the target orientation and convergence speed. Thirdly, the polynomial smoothing optimization function is used to prune redundant branch paths and improve the smoothness of planned paths. Finally, experiments are carried out to verify the proposed method. Results show that errors between the actual path and the planned path of CCDMs are less than 1.055 mm. In that case the feasibility of the AS-RRT method for path planning of CCDMs is verified. In addition, the method is applicable not only to CCDMs, but also to many cable-driven manipulators with similar configurations.

In this paper, for the problem of irregular wear clearances in planar multilink mechanism, dynamic model as well as reliability model of kinematic accuracy are proposed. The worn kinematic joint undergoes surface reconstruction, and an analysis is conducted on how varying friction coefficients and initial clearance values influence the mechanism’s dynamic characteristics after wearing. Firstly, utilizing the Lagrange multiplier method, a rigid-body dynamics model for the mechanism that includes multiple revolute joint clearances is developed. Secondly, a wear prediction model for the revolving joint clearance is formulated utilizing the Archard wear model, and a rigid-body dynamics modeling approach is proposed for the multi-link mechanism characterized by multiple revolving joint wear clearances. Subsequently, based on first-order second moments method and the strength-stress interference model, the failure conditions are defined and the kinematic accuracy reliability model of a planar multi-link mechanism containing multiple irregular wear clearances is established. Through an analysis of wear characteristics across varying friction coefficients and initial clearance values, intricate relationship between friction coefficient and wear is elucidated, and impact of initial clearance values on wear characteristics. In addition, the proposed method is verified by ADAMS. Considering the extensive utilization of multi-link mechanisms in real-world applications, the developed methodology exhibits broader generalizability. This study integrates the Archard wear model with the Lagrangian multiplier method to establish a dynamic model accounting for multi-clearance irregular wear. This integration not only enables the prediction of wear effects on mechanism dynamic characteristics but also facilitates the analysis of post-wear dynamic responses and nonlinear behaviors. By further studying the influence of the wear clearance on the nonlinear dynamic characteristics of the mechanism and analyzing the reliability of the motion precision of the mechanism, the theoretical basis and practical guidance for the design and maintenance of the mechanism are provided.

In this article, we studied the electromagnetic field and ramp type heat source on waves propagation in semiconductor nanostructure thermoelastic solid. A generalized thermoelastic theory along with coupled nonlocal elastic theory considered mathematical model representing the phenomena is formulated. Incorporating a ramp type heat equation of fractional order allows us to point out the influence of temperature on wave motion. The governing equations are decomposed into their longitudinal and transverse components using the decomposition method. It is obvious that one longitudinal P-type and secondary shear S-type three waves are propagating through the medium. For a given material, analytical results for the reflection coefficient of each of the transmitted waves are computed numerically and then displayed graphically. The influence of electromagnetic field, nonlocal parameters ({{e}_{0}}a) and time derivative fractional order (FO)(alpha ) are also discussed. Previous results produced with the electromagnetic field ignored have been compared and also with the previous investigations. The results conclude that the results obtained agreement with the physical meaning and applicable on diverse field as geophysics, geology, acoustics, engineering, and aerospace.

This study utilizes machine learning (ML) methodology to estimate the stress intensity factor (SIF) for multiple edge cracks in a coating-substrate pair. The arbitrarily varying loading function is decomposed into a weighted sum of sine and cosine functions using Fourier series expansion, from which extracted are the characteristic period and harmonic number. A large data set derived from finite element calculation is used to train the ML model. By validation and comparison, it is found that the even extension method offers the highest accuracy in estimating the SIF. For three different loading functions, the predicted results show an average error of less than 1% compared to those by the finite element method. Additionally, the error of the predicted results is less than 3% in comparison with those in two thermal shock scenarios from existing literatures. The findings highlight the potential of ML-driven computational frameworks to achieve efficient and accurate evaluation of SIF for multiple cracks under realistic service conditions.

This study investigates the ballistic performance of aluminum alloy protective plates under projectile impact, focusing on thickness effects and projectile head geometry. By analyzing high strain rate responses, it reveals the sensitivity of deformation characteristics and failure mechanisms to structural parameters. To address the challenge in describing aluminum’s unique mechanical behavior during ballistic tests, the work systematically reviews applicable constitutive models and damage criteria. Furthermore, it evaluates predictive models for ballistic limits and energy absorption, providing theoretical support for understanding aluminum alloy behavior under complex impact conditions. The synthesized modeling approaches effectively resolve prediction difficulties in high-strain-rate scenarios with multiaxial stress states.

A linear system of classical and hyperbolic thermoelasticity has been established in the framework of the Caputo time fractional derivative in the cartesian domain. The solutions of the homogeneous time fractional system of classical and hyperbolic thermoelasticity with respect to initial conditions are obtained by applying the fractional natural decomposition method (FNDM). The convergence of infinite series solutions has been addressed. The stability conditions of the proposed systems are discussed. Furthermore, the physical behavior of the acquired solutions has been represented in the form of graphical representations for different fractional orders. The obtained results of the study demonstrate the FNDM’s high accuracy and computational effectiveness. Moreover, the significant role of relaxation time and the fractional order parameters are studied as material characteristics.