Archive of Applied Mechanics最新文献

This research adopted a micromechanical modeling approach to elaborate the debonded layered structure behavior under the combined mechanical and hygro-thermal loading. The structural distortion under the combined loadings has been modeled through Green’s strain and Lagrangian reference frame. In addition, the structural deformation has been modeled using two types of kinematic models with and without stretching term effect. Moreover, the corrugated composite properties are evaluated with the help of a micromechanical model due to the hygro-thermal effect considering the individual volume fractions and moisture retention ratio. The final form of governing equations is obtained using variational technique and solved numerically (finite element steps and direct iterative method). The model validity and its repeatability are verified through the comparison study. The predicted numerical response differs from the literature data by a minimum of − 1.39% and a maximum of − 16.08%. Finally, a set of numerical examples has been solved to elaborate on the model’s adequacy and investigate the influence of delamination, environmental effects, and other input parameters related to the geometrical details of the composite components. Delamination in the curved panel affects linear and nonlinear dynamic responses regardless of size, position, or location. An increase in fiber volume fraction and aspect ratio (a/b) reduces both higher-order models dynamic linear and nonlinear responses.

It is necessary to accurately and efficiently calculate the wrinkling stresses of sandwich panels under in-plane compression. However, the simple equations used in engineering may obtain inaccurate results, whereas finite element methods with higher accuracy may be computationally expensive. This study proposes a new method for solving the wrinkling problem of sandwich panels using structural optimization theory at a low computational cost. A sandwich panel was divided into several virtual plies, which were assigned design variables to describe the vertical displacement during wrinkling. The wrinkling stress was obtained by minimizing the admissible in-plane compressive stress. The method was verified using finite element and experimental methods, as good agreement was found. The differences were less than 5% and 20% with the finite element and experimental results, respectively. Moreover, this method can easily compute the wrinkling stress of sandwich panels with functionally graded material cores with a little increase in computational cost. This method allows engineers to compute the wrinkling stress effectively and efficiently without the need for complex numerical models.

Self-actuated oscillation systems possess the unique ability to extract energy from their surroundings to sustain oscillation autonomously, which makes them ideal for applications in soft robotics, active actuators and smart devices. In contrast to conventional materials, mechanical metamaterials, known for their negative Poisson's ratio and volume expansion properties, can boost the functionality and performance of self-actuated systems. This theoretical study proposes an electrothermally-induced self-actuated oscillation system in liquid crystal elasomter (LCE) mechanical metamaterials under steady-state circuits and investigates its self-actuated mechanism and behavior. The electrothermal effect caused by the external electrical circuit enables LCE fibers to do net positive work. When the net positive work done by LCE fibers exactly compensates for the damping dissipation of the system, self-actuated oscillation can be triggered and maintained. The results indicate that self-actuated oscillation can be modulated and controlled by system parameters. The procedure can pave the path for designing active micromachine, energy harvester, medical devices and monitoring sensors.

This research presents an in-depth exploration of the vibrational performance exhibited by sandwich beams with variable thickness profiles. These beams undergo a gradual reduction in thickness along their length. The core material of these sandwich beams is constructed from FG cellular materials, while the facesheets are reinforced with carbon nanotubes. Due to the varying distribution patterns of these reinforcements concerning the beam’s height, it becomes essential to apply stress transformations at specific angles to accurately compute the equivalent material properties. The study employs both Hamilton’s principle and variational approach to derive the governing equations for motion, as well as the associated boundary conditions. To comprehensively assess the effects of various parameters such as geometry, porosity coefficient, diverse distribution patterns of porosity and carbon nanotubes, as well as the transformation angle on the natural frequencies, a robust numerical technique known as the differential quadrature method is employed to solve the derived equations. It is found that compared to beams with a constant thickness, tapered beams typically display lower frequencies. Also, if the reinforcements are not arranged in the upper and lower layers in the direction of changing the thickness, the results will have noticeable changes.

This study investigates the two-dimensional deformations within the framework of the two-temperature thermoelasticity theory, focusing on the interplay between laser pulse heating, acoustic pressure, and the resultant elastic material response. Our exploration is centered on the understanding of how acoustic waves, generated by laser pulses, influence the thermoelastic and mechanical behavior of materials. The role of acoustic pressure in modulating the thermoelastic response during laser pulse heating is investigated. Theoretical formulations are developed to describe the coupled evolution of temperature and deformation fields in the two-dimensional (2D) space. Employing normal mode analysis, the exact solutions of the main variations (wave propagation) of physical fields are obtained. Some boundary conditions are utilized for more accurate numerical simulations. The numerical results are discussed theoretically and the wave propagation of the physical quantities under study is represented graphically. The results obtained from this study have significant implications for various applications, including laser material processing, biomedical procedures, and non-destructive testing.

In this work, a heat conduction model is generalized by employing the time-fractional heat conduction and nonlocal strain theory. In order to conduct a qualitative analysis of the problem, a half-space subjected to thermal shock is studied. For the convenience of obtaining numerical results, Laplace transform is used and analytical solutions in the Laplace domain are obtained. Solutions in the time domain are then obtained by Laplace inverse transform. Numerical results show that fractional order parameters have a relatively small influence on displacement but a larger influence on other quantities; nonlocal coefficients have a significant influence on all quantities; as time increases, the response of each quantity becomes more obvious; the strain relaxation coefficient has a small influence on temperature but a larger influence on other quantities. It is therefore necessary to consider the fractional theory generalized in this work in practical engineering problems and in the design of materials with heat conduction.

In this research, the thermally induced vibration of the plates on the elastic foundation has been investigated. The plate is made of functionally graded materials (FGMs) that is graded along the thickness. All mechanical and thermal properties dependent on temperature are taken into account. To apply the temperature dependence of thermomechanical properties, the well-known Touloukian equation is used. The two-parameter elastic foundation, Winkler–Pasternak, is considered to be linear, isotropic, and homogeneous. The general formulation and equations governing the phenomenon of thermally induced vibration have been written under the assumptions of linear uncouple thermoelasticity. The one-dimensional transient heat conduction equation has been discretized with the help of the finite element method in the direction of thickness, and it has been solved over time by applying the Crank–Nicolson method. Also, the thermally induced force and moment resultants in each time step have been calculated based on the temperature profile. To obtain the equations of motion, Hamilton’s principle based on the first-order shear deformation theory has been used, and the obtained equations and boundary conditions have been discretized by applying the generalized differential quadrature (GDQ) method and solved by using Newmark time marching scheme.

The applications of piezoelectric materials in the field of smart structures have received significant attention from both the communities of science and engineering. Numerous experimental studies have been carried out to endow smart structures with good flexibility. The flexible/stretchable piezoelectric materials are developed to fit this emerging trend. Generally, these materials undergo significant deformation before reaching fracture failure, and they often exhibit a stress-softening phenomenon during the deformation process. However, the traditional linear constitutive model, typically used for rigid piezoelectric ceramics, continues to dominate theoretical and modeling processes in many scenarios. Existing nonlinear constitutive models usually introduce additional coefficients besides elastic, piezoelectric, and dielectric coefficients. Determining these coefficients requires a substantial number of experiments. In this work, based on a Neo-Hookean material model and electromechanical theory, a novel model for flexible piezoelectric material considering large deformation has been established. In contrast with existing models, the present model describes the nonlinear behavior of flexible piezoelectric material without the need for introducing additional parameters. Furthermore, this model exhibits a quadratic dependence of stress on the electric field. To facilitate practical applications, the constitutive model has been implemented using the commercial simulation software ABAQUS through a user subroutine. The accuracy of the subroutine is validated by comparing simulations with analytical solutions for uniaxial stretching of a flexible piezoelectric ribbon. Several numerical examples are followed to demonstrate the robustness of the elements. The proposed model offers a valuable tool for the analysis and design of flexible piezoelectric material.

Dynamic damage constitutes a significant factor influencing engineering safety. Constitutive models predicated on statistical distribution demonstrate a capability in accurately representing the dynamic failure process of rocks. This study employs the high-strain-rate Hoek–Brown criterion to delineate the strength characteristics of rock microelements, subsequently establishing a novel dynamic statistical damage constitutive model based on statistical damage theory. Firstly, the model’s validity was corroborated using test data from different rocks (sandstone, granite, and marble) under varying confining pressure conditions. Subsequently, the influence of parameters F₀ and m on the stress–strain curve was discussed. Finally, the relationships between the Hoek–Brown criterion parameters ((sigma_{{cdot{varepsilon }}}), (m_{{dot{varepsilon }}})) and the strain rate for different rocks were analyzed. The findings suggest that the model effectively characterizes the stress–strain relationship during the dynamic failure process.