Mechanics of Solids最新文献

This study examines the planar harmonic waves reflection from a rotating semi-infinite elastic material with a gravity using the generalized thermoelasticity theory. The ratios of reflected wave amplitudes to incident wave amplitudes are called reflection coefficients, and they are computed. The impact of rotation and gravity on the reflection coefficients is graphically represented and the numerical solution is executed. The predictions of the Lord–Shulman and dual-phase-lag models are compared in the absence and presence of rotation and gravity. The rotational and gravitational field impacts explain the coefficients of waves reflection on the free surface of the half space. A comparison between the present results and the previous investigation indicate to the strong effect of the external parameters on the phenomenon and agree with the practical results.

Rotor shaft cracks can be acknowledged as a substantial issue regulating the reliable and safe machines operation. When the crack has grown and is not discovered, unexpected catastrophe may happen, ultimately resulting the plant being shut down with numerous losses attached. When the rotor shaft is revolving in a viscous fluid environment, it becomes exceedingly challenging to analyze the size and position of the crack. In the present research work, a novel hybridized technique a clonal selection algorithm (CSA) with a differential evolution algorithm (DEA) is proposed for early detection of multiple transverse cracks and its position in the rotor shaft rotating under altered viscous fluid environment in an acceptable amount of time limit. Relative natural frequency at x-axis, relative natural frequency at y-axis, relative amplitude of vibration at x-axis, relative amplitude at y-axis and viscosity of fluid are use as input parameter and relative crack depth and crack location are used as a output parameter in the hybrid technique. To compute the amplitude and natural frequency of the cracked rotor shaft rotating under different fluid environment utilizing the stiffness matrices of crack element. An external force of fluid is computed by Navier–Stokes equation. Theoretical evaluation was executed using Matlab. To authenticate the theoretical and experimental value of natural frequency and amplitude, perform the finite element analysis by using ANSYS. For training the hybrid system, the amplitude and natural frequencies are found out using theoretical, experimental and finite element analysis for different crack depth and positions. The test results of the recommended hybrid technique are compared with finite element analysis and experimental analysis for validation, and satisfactory outcomes have been observed. Therefore the recommended hybridized CSA–DEA technique would establish an effective tool for real-time crack detection in rotor.

This investigation aims to develop a thermoelasticity model to analyze the propagation of thermoelastic waves in a composite hollow circular cylinder with an LEMV/CFRP interface layer. The model integrates a modified non-local couple stress theory to address challenges related to higher-order time derivatives. The derivation yields three partial differential equations governing the modified non-local couple stress of the cylinder in axisymmetric mode. By applying linear elasticity theory, these equations are solved to derive frequency equations for the cylinder’s external surface under traction-free conditions while ensuring boundary continuity. The study investigates how variations in wave number and thickness affect the frequency, temperature, and displacements within the field. To evaluate the impact of different thermoelasticity theories and non-local coupled stress parameters, the research employs tables and graphs for comparison and estimation. These visual aids provide valuable insights into the behavior of the composite cylinder across various scenarios.

The article presents an analytical solution for the problem of a circular pipe turning inside out in a rigid gasket. Formulas for the magnitude of the radial stress, which is responsible for the adhesion between the pipe and the gasket, have been obtained. The solution is obtained for an arbitrary incompressible hyperelastic material with a hyperelastic potential that depends only on the first invariant of the left Cauchy–Green deformation tensor (various generalizations of the neo-Hookean solid) or on the second invariant of the logarithmic Hencky strain tensor (various generalizations of the incompressible Hencky material). The solution considers the occurrence of plastic flow in areas adjacent to the lateral surfaces of the pipe. Both ideally plastic and isotropically hardening materials of a general type are considered. For the latter, a solution scheme is given; in the particular case of a linearly hardening material, a closed-form solution is obtained. For the perfect plasticity model, a closed-form solution was obtained for the neo-Hookean solid, for an incompressible Hencky material, and for the Gent material.

Based on experimental data on the destruction of the adhesive layer that interfaces two plates in a given area, and the well-known analytical solution corresponding to the design scheme, variants of the destruction criterion are considered, taking into account hydrostatic pressure and invariant components of elastic energy. One- and two-parameter criteria are studied, in which the products of the deformation energy of volume and shape and the layer thickness form the critical flow of elastic energy density. It is shown that the loosening of a thin adhesion layer with a two-parameter criterion quasi-linear with respect to the deformation energy of the volume most accurately describes the critical state.

Artificial intelligence has been widely used in engineering. In this paper, we propose to combine the backpropagation neural network (BPNN) with the refined plate model based on Carrera Unified Formula (CUF) to advance the development of damage detection. The prediction model is built by utilizing the error back propagation function of the neural network. In addition, MATLAB uses Taylor’s interpolation algorithm and lower degrees of freedom yet achieves the same accuracy as ANSYS, and the improved plate model accurately reproduces the mechanical properties of the metal plate. A database is then built based on the mechanical model to detect the location of damaged elements and node displacements. The nodal displacements were used as inputs while the locations of damaged elements were used as training outputs for the neural network. The effectiveness of the proposed method was verified through various damage scenarios. The results show that the method can accurately predict individual damage locations based on node displacements alone. The neural network combined with the plate model achieved a detection accuracy of 91% with a regression coefficient of 0.95.

In this work, a novel model is presented that might explain the occurrence of elastic-mechanical-thermodiffusion (EMTD) waves in microelongated semiconductors. When analyzing the optoelectronic impact of laser pulses on a semiconductor material, it is important to take into account the interaction between holes and electrons. As a function of the thermal effect, thermal conductivity may be chosen. The photothermal (PT) theory and the thermoelasticity (TE) theory are used to decompose the governing equations with the temperature gradient. The fundamental equations are explained in terms of a one-dimensional (1D) thermoelastic (TED) and electronic (ED) deformation. The Laplace transform is a mathematical tool for obtaining the main physical fields. Some boundary conditions are taken at the free surface, and they are crucial to the technique by which the issue is solved. The Riemann-sum approximation technique is used to invert the Laplace transform to find the field solutions in the closed space-time domain. The mechanical ramp type of boundary conditions is used. Some comparisons are done under the influence of laser pulses and changing thermal conductivity and variable thermal memory based on numerical data and graphical representations of silicon material.

The thin composite von Kármán plates in postbuckling are considered. Using the first Piola stress tensor and the displacement gradient tensor, the complementary energy variational theorem is proven. The Kirchhoff assumptions are adopted. The plate lay-up is symmetric and pointwise. According to the theorem, at the actual stress state of the plate the complementary energy (as a functional of the internal forces and of the moments) reaches its stationary value. The stationary feature of the actual state is valid as compared to other feasible states satisfying the static equilibrium and the static boundary conditions. The theorem is a consent of the static variational principle. The principle leads to the linear relations between forces/moments, created by the corresponding first Piola stress tensor components, and the 2D-strains/curvatures. An illustrative plate example is given.

A generalized two-temperature thermoelastic model with a memory-dependent derivative has been constructed for a two-dimensional magneto-thermoelastic problem interacting in an isotropic homogeneous, perfectly conducting semi-infinite medium under the fuzzy environment. The thermophysical fuzzy variables like displacement, temperature, and other variables are considered in r-cut form. The theoretical solutions of coupled partial differential equations are calculated in the combined Laplace–Fourier transformed domain using the eigenvalue approach under the traction-free boundary and thermal shock, which is dependent on time. Numerical results of thermophysical fuzzy variables are illustrated graphically for varying parameters such as time delay, kernel functions, and time and are compared with their respective crisp plots. The real-life applications and conclusions based on analytical and numerical results are discussed later on.

In mechanical systems, the machining surfaces of various components, especially those subjected to precision machining such as the roller and track surfaces in feed systems, often exhibit non-Gaussian roughness characteristics, which significantly differ from the Gaussian surface model widely adopted in traditional contact models. In order to thoroughly investigate the influence mechanism of characteristic parameters of non-Gaussian rough surfaces on the contact performance of mechanical interfaces, this study specifically constructs a contact model for non-Gaussian rough surfaces. This model elaborately elucidates the complex effects of skewness and kurtosis, two key parameters, on contact force, actual contact area, and contact stiffness. Thus, it deepens the understanding of contact characteristics of non-Gaussian rough surfaces and provides a theoretical basis for the analysis and optimization of the contact performance between rollers and tracks in feed systems.