Mechanics of Solids最新文献

The diamond lattice structure is a type of lattice structure that exhibits excellent isotropic and mechanical properties. The variable section design can optimize the section size of the support rod of lattice structure and improve the mechanical properties of lattice structure. In this paper, a design method of variable section diamond lattice structure based on minimal surface parallel implicit function is proposed. The parametric variable section design of lattice structure can be realized by adjusting the variable section coefficient K. A functional relationship between the K value and the cross-sectional radius of the struts is established, and a mechanical analytical model of the variable cross-section diamond lattice structure is constructed based on Timoshenko beam theory. Using SLM (selective laser melting) technology, six lattice structure samples made of 316L stainless steel with a volume fraction of 5% were prepared and subjected to compression tests. The results show that the mechanical properties of the lattice structure first increase and then decrease with the increase of the variable cross section coefficient K. Compared to constant cross-section structures, the variable cross-section lattice structure’s effective elastic modulus can be increased by up to 20.23%, and the effective yield strength can be increased by up to 14.79%.

Ground vibration is a crucial foundation for the study of blasting demolition and rock-soil failure. In this paper, a soil-layer coupling model is established using the discrete element method (PFC3D), which takes distribution of microscale features into account. Subsequently, based on the Mindlin solution in an elastic half-space subjected to concentrated forces, the difference between the theoretical and numerical solutions is validated, and this study further investigates the laws on impacting vibration responses. The results reveal that, under the impact action of falling hammer, the vibration velocity of soil particle approximates a triangular function over time. The vertical stress exhibits a distribution pattern of increasing initially with soil depth and then decreasing. The contact force chains disperse in a ‘root-like’ manner, leading to a tendency for shear failure in the soil. Actually, impact vibration is a process of accelerated energy conversion, with the majority of impact energy dissipated by various forms of damping. This method can provide a theoretical basis for the stability analysis of ground vibration and disaster prediction.

The present study envisages on the mathematical modeling and analysis of the dispersion relation of surface waves and in particular Stoneley wave, in a diffusion media homogeneous thermoelastic material having boundary conditions. Adoption of the harmonic method of wave analysis, non-dimensional of the derived equations of motion and boundary conditions produced by the model are also encompassed in this study. The Stoneley waves propagation at the interface between two-thermoelastic diffusion solid half spaces considering Green–Nagdhi models of thermoelasticity (type-II as well as type-III) [1, 2] is studied. The dispersion equation of Stoneley waves is derived in the compact form by using the appropriate boundary conditions. Furthermore we use the numerical methods and computations to calculate the propagation characteristics like determinant magnitude, Stoneley wave velocity and attenuation coefficient. The obtained numerical results are depicted graphically. Some special cases are also discussed. This study formulate a novel governing equation for an interface of two thermoelastic media with diffusion, the Stoneley waves significance and investigating the influence of wave number, wavelength and phase velocity. A comparison made between the previous results obtained and the present study that indicates to the strong impact for the external parameters and applicable in diverse related fields as geology, biology, engineering, and astronomy.

The reconfigurable parallel robots are highly adaptable to different tasks and environments, making them suitable for a wide range of industrial and medical applications. Optimizing the geometrical and structural parameters is a crucial aspect of designing a parallel robot. However, due to different degrees of freedom and workspaces, the optimization of reconfigurable parallel robots is a challenge. This paper presents the design, unified dynamic modeling and multi-objective optimization methodology of an innovative 3UPS-PU/S robot. This parallel robot can be reconfigured from a Tricept mechanism into a fully spherical mechanism through the reconfiguration of the PU/S central passive limb. For this purpose, the unified dynamic model of the robot is derived. With respect to workspace, manipulability and dynamic dexterity, three performance indices are considered as the objective functions. The robot is optimized with respect to the design and geometrical constraints using the non-dominated sorting genetic algorithm II (NSGA-II), which is used to find the Pareto fronts. The obtained solutions are a set of optimal geometric parameters to adjust the kinematic and dynamic performances. The results depict that the process effectively identified a 3UPS-PU/S robot with an efficient dexterous workspace. Also, based on the optimization results a prototype of the robot was fabricated. Overall, this paper provides a novel framework for the multi-objective optimization of reconfigurable parallel robots.

The SH waves in a rotating functionally graded system comprising an elastic substrate and functionally graded magneto-electro-elastic layer are studied analytically. The bonding of layer and substrate are well contact with corrugation as well as upper boundary taken as corrugated with stress free. Dispersion relations have been obtained for four cases of electrically open and magnetically open, electrically short and magnetically short, electrically open and magnetically short, and electrically short and magnetically open situations with corrugated interface. Based on the numerical results, the properties of SH waves through the proposed framework and the conditions depending on various physical and geometrical parameters have been examined. The study examines the simultaneous simulated results of several physical parameters, including inhomogeneity, layer thickness, rotation, and amplitudes of corrugation, which were created using Mathematica 7. The examined model could be helpful for the development of surface acoustic wave (SAW) devices.

The study investigates thermal and elastic interactions in isotropic microplate resonators with elastic and viscous properties, exhibiting Kelvin–Voigt behavior, under a uniform magnetic field. Using the modified Moore–Gibson–Thomson thermoelastic theory (MGTE), modified couple stress theory (MCST) and the Hamiltonian principle, the differential equation of motion, including size effects, is derived. The model examines thermoelastic vibrations of a circular microplate with simply supported edges and various boundary conditions. The influence of length scale factors on the bending behavior of thermo-viscoelastic microplates is analyzed. Results show that microplates modeled with MCST theory are more rigid than those with standard continuum plate theory, aiding in the design of high-quality, low-energy-dissipation micro/nanosheet circular resonators. These findings are crucial for modern engineering, providing insights into thermoelastic coupling and enhancing microplate-based system performance and efficiency in various applications.

Triple-porosity models provide a possibility to investigate the significant problem in some natural sciences and engineering fields. These media often consist of different scale fractures/cracks with different permeability embedded in a matrix with low-permeability pores. In this paper, the phenomenological equation for the elastic wave propagating in a fluid-saturated triple-porosity medium is developed based on the Lagrangian method. The mass coefficients in kinetic energy and drag coefficients in dissipation energy are obtained by reducing them to single- and double-porosity cases. The plane wave analysis shows that there are four compressional waves and one shear wave, namely, one more compressional wave is generated comparing with the double-porosity model. The dispersion and attenuation of the compressional and shear waves at multiple frequencies are analyzed based on the numerical results. It is observed that the first compressional wave has two attenuation peaks, namely, one more attenuation peak is observed comparing with the double-porosity case.

The present investigation deals with the rotation of magneto-thermoelastic solid with voids due to laser pulse and memory-dependent derivative in the context of a three-phase-lag model of generalized thermoelasticity. The bounding plane surface is heated by a non-Gaussian laser pulse and is subjected to prescribed stress. The entire porous medium is rotated with a uniform angular velocity. The normal mode analysis technique has been incorporated to solve the physical problem to obtain the exact expressions for the displacement components, stresses, temperature distribution, and change in the volume fraction field to represent the thermo-physical quantities graphically in the presence and the absence of rotation and magnetic field. The effect of linear and nonlinear kernel function and the effect of the delay-time parameter are also reported.

This study utilizes a multiple scales perturbation approach to analyze the nonlinear wave propagation characteristics of a doubly curved sandwich composite piezoelectric shell with a flexible core under hygrothermal conditions. Stress and strain computations for the flexible core and face sheets are conducted employing Reddy’s third-order shear deformation theory (TSDT) and third-order polynomial theory, respectively. The investigation delves into the combined effects of a multilayered shell, flexible core, and magneto-rheological layer (MR) in elucidating the nonlinear behavior of both in-plane and vertical moments within the core. The Halpin-Tsai model is employed to derive the properties of polymer/Carbon nanotube/fiber (PCF) and polymer/Graphene platelet/fiber (PGF) three-phase composite shells. The governing equations for the multiscale shell system are derived using Hamilton’s formulation. The study explores temperature fluctuations, diverse distribution patterns, curvature ratios, and electric fields through numerical analysis, with graphical presentation of results. Previous research has validated the accuracy of these methodologies. Notably, these factors significantly impact the frequency-amplitude curves of the smart structure.

The problem of dispersed failure of isotropic and cylindrical-anisotropic rods made of damageable materials during torsion has been investigated. Non-linear differential equations have been formulated, representing the expansion of dispersion front during torsion of rod transmitting power under a constant torque. For the development of dispersed failure process, formulas have been obtained to identify incubation period and, the problem has been resolved.