Acta Mechanica最新文献

We consider the problem of modeling thermoelastic nanobeams that dissipate thermal energy by radiation. The proposed study focuses on one-dimensional nanostructures whose mechanical behavior is described by a nonlocal elasticity theory and modeled through the Rayleigh beam theory, which includes the effects of rotary inertia. Thermal energy exchange with the environment is accounted for by employing an extended form of the Green Naghdi type II theory of thermoelasticity, which allows the modeling of radiative effects without resorting to classical Fourier diffusion. The coupled thermoelastic system is solved under wave-form assumptions, allowing for the emergence of damped wave phenomena induced by the radiating effects. The results highlight the differences between the Rayleigh and Euler Bernoulli formulations, especially in the local regime, and confirm the presence of dissipative behavior in terms of wave speed attenuation and damping over time. Although the model is linear, the structure of the dispersion relation reflects features typically associated with nonlinear responses, such as amplitude-dependent wave attenuation. This provides a foundation for future nonlinear extensions in thermomechanical nanobeams, in line with recent advances in nonlinear nanomechanics. The model may be suitable for applications in nanoengineering fields where temperature effects on mechanical response are non-negligible, such as nanosensors and thermomechanical actuators.

This study investigates the electromechanical dynamic behavior of the three-layered flexoelectric microshell, where the middle layer consists of the porous functionally graded (FG) distribution of silica and alumina, while the inner and outer layers are homogeneously composed of barium titanate. The displacement field is developed based on the first-order shear deformation theory (FSDT), and the reformulated flexoelectric theory is employed to derive the structural relations of the microshell. Governing equations and corresponding boundary conditions are extracted within the framework of Hamilton’s principle. Subsequently, the equations are solved in spatial and temporal domains under the considered boundary conditions using the finite element method and Newmark-beta method. The effects of various parameters, including the velocity of the load (v_P), FG power (N), flexocoupling coefficients (f_i), size effect (l_i), porosity effect (ϕ), electrical size effect (β_i), and flexoelectric layer thickness (h_f), on the electromechanical dynamic behavior of the microshell are studied. The results indicate significant influences of these parameters on mechanical components, such as deflection, and electrical components, such as electric field intensity.

We use Suo’s complex variable formulation to derive a closed-form solution to the plane strain problem of a compressible liquid inclusion of arbitrary shape embedded in an infinite degenerate orthotropic elastic matrix subjected to uniform remote in-plane stresses. The one-to-one mapping function that maps the exterior of the liquid–solid interface onto the exterior of the unit circle in the image plane contains an arbitrary number of terms. Using a varied form of analytic continuation, a set of linear algebraic equations with quite simple structure is obtained. Once the set of linear algebraic equations is solved, the internal uniform hydrostatic stress field within the compressible liquid inclusion and the elastic field in the degenerate orthotropic elastic matrix characterized by a pair of analytic functions are completely determined.

We study thermally induced redistributions of free carriers in thermopiezoelectric semiconductor plates with flexoelectric effects. A new plate model is developed by integrating the thermopiezoelectric semiconductor theory with flexoelectric effects, Kirchhoff plate theory, and the principle of virtual work applicable to semiconductors. This model comprehensively accounts for the effects of piezoelectric, flexoelectric, strain gradient, temperature and semiconducting, presenting the boundary value problem that includes the field equations and all relevant boundary conditions. To validate the efficacy of the new model, we analytically solve for electric potential and concentration perturbations in a simply supported plate under temperature changes in in-plane and transverse directions. The results reveal that varying the modes, amplitudes, and directions of the prescribed temperature fields enables tuning of the electric potential distribution and the redistribution of free carriers. Moreover, the electric potential and free carriers concentration perturbations calculated with the current model are found to be lower than those of the piezoelectric semiconductor plate under in-plane temperature change. Notably, the transverse electric potential is particularly affected by temperature changes in in-plane and transverse directions. This work provides novel guidance for the design of semiconductor devices aimed at thermal applications.

Energy dissipation and frequency shift (FS) due to the thermoelastic coupling (TEC) restrict the improvement of resonator quality factor (Q-factor). However, the mechanisms in functionally graded materials (FGMs) micro-resonators are unclear because of the complex nonlinear TEC equations and scale-dependent effect. This paper presents a TEC model for FGMs circular plates based on the surface elasticity theory (SE theory) and the nonlocal dual-phase-lagging heat conduction model (NDPL model). The layered homogenization method is used to solve the nonlinear heat conduction equation arising from the variation of material components along the plate’s thickness in a power-series form. An analytical solution for the resonant frequency is obtained by exploiting the similarity between the nonlinear TEC vibration equation of FGMs circular plates and that of homogeneous circular plates under adiabatic conditions. The analytical solutions for thermoelastic damping (TED) and FS of FGMs circular plates are derived. The reliability of the layered homogenization method is verified by numerical result stability. Numerical results show that the functional gradient index and scale-dependent effect such as nonlocal thermal parameter significantly influence the TEC behavior of FGMs circular plates. When considering the scale-dependent effect, the reduction amplitudes of TED, FS, and frequency attenuation (FA) of the FGMs plate are lower than those of the full N₃Si₄ plate and the full Ni plate, namely, compared with isotropic homogeneous circular plates, FGMs circular plates have a lower FS amplitude and better thermal dissipation adjustability, thus offering higher operating accuracy. These findings are crucial for improving micro-resonator design accuracy.

In this study, a novel numerical framework is introduced, designed to conduct static analyses of laminated composite plates, with a focus on both global and local behaviors. The main objective is to develop an efficient computational method capable of providing accurate results while minimizing computational resources. This is achieved by making use of the refined zigzag theory, which captures layer-wise local deformations, with the advanced finite element technique known as the cell-based smoothed discrete shear gap. The integration significantly enhances computational efficiency for refined zigzag formulations. Various response quantities such as deflection, in-plane displacement, normal stress, and transverse shear stress are assessed. These investigations encompass a range of laminate configurations including cross-ply, uniaxial-ply, and angle-ply arrangements. To validate the accuracy of our method, numerical results are compared with analytical solutions. In addition, a convergence study is conducted to demonstrate the effectiveness of the present formulation. The numerical findings not only demonstrate the method’s capacity for sufficiently predicting static responses but also showcase its potential for practical applications in engineering design and structural analysis.

This study examines the static flexural response of composite panel reinforced with graphene origami patterns under combined thermal and mechanical loadings. A kinematic framework incorporating shear deformation forms the basis for deriving the system's governing equations. These equations, expressing relationships between in-plane displacements and rotational degrees of freedom, are formulated using the virtual work principle. The associated boundary conditions are derived using the virtual work principle. Constitutive relations are established by determining the effective thermomechanical properties of the copper matrix composite containing graphene origami nanofillers, applying validated micromechanical methods. An analytical solution framework employing Navier's method is developed to solve the governing equations. Results detailing deformation, strain distributions and stress fields through the shell thickness are presented as functions of the foldability parameter. The main novelty of this work is investigating the stress, strain and deformation variations with changes of folding parameter along the thickness direction. Because of the simultaneous changes of the all materials properties and strain components, the stress variation needs a comprehensive investigation as presented in the paper. Analyses reveal that increasing the foldability parameter induces greater displacements and stresses. This trend is attributed to a corresponding reduction in the overall structural rigidity of the graphene origami reinforcement.

Recently, artificial neural networks (ANNs) have shown strong performance in impact load identification. However, model training and load identification remain time-intensive. To solve this, we propose a method based on kernel extreme learning machine (KELM) for impact load identification and optimize the key parameters of KELM using sparrow search algorithm (SSA). Compared to deep learning models like convolutional neural networks (CNNs) and recurrent neural networks (RNNs), KELM significantly enhances training and identification speeds while maintaining high accuracy. We validated the method with simulation data from a three-degree-of-freedom (3DOF) system and experimental data from a double-clamped beam. Results indicate that KELM offers higher accuracy in identifying impact loads compared to CNN and RNN. Meanwhile, this method also significantly improves model training and load identification speeds. Further validation with data from a pumped liquid rocket engine confirms its effectiveness for complex load paths in intricate structures, making it a promising tool for real-time impact load identification in engineering applications.