International Journal of Mechanics and Materials in Design最新文献

This paper presents a novel thermoelastic model designed to analyze the behavior of porous materials containing voids. The proposed model extends the two-phase lag theory (TPL) by incorporating inherent delays in thermal responses specific to such materials. A significant advancement over traditional elastic models is the inclusion of both spatial and temporal nonlocal effects, which are essential for accurately capturing the intricate microscopic interactions characteristic of porous structures. Furthermore, the integration of fractional Caputo-tempered derivatives into the heat conduction equation enhances the representation of memory effects, offering deeper insights into how prior deformations and thermal influences shape material behavior. The validity and applicability of the model were demonstrated through a detailed analysis of the transient thermo-mechanical response of an infinite porous body with a cylindrical cavity subjected to a time-dependent heat flux. Results were compared with findings from existing literature, enabling an evaluation of the effects of nonlocal interactions, phase delays, and fractional parameters on the observed responses. This comprehensive approach provides a more refined understanding of the dynamics of porous materials under combined thermal and mechanical loads, advancing the theoretical framework for such materials.

This study presents a novel spatiotemporal nonlocal elasticity model based on the Klein–Gordon-type theory to investigate size- and time-dependent mechanical and thermal behaviors in perfectly conducting isotropic micropolar thermoelastic materials at micro- and nanoscales. The proposed model integrates internal length and time scales to account for nonlocal interactions and long-range forces, which are essential for accurately describing material behavior at reduced scales where classical continuum theories fail. This framework is seamlessly coupled with the dual-phase-lag (DPL) generalized thermoelasticity to capture finite-speed heat propagation, overcoming the limitations of Fourier’s law. To analyze the coupled thermoelastic responses, we apply the normal mode analysis technique, which allows for the derivation of exact analytical solutions for critical field variables—including temperature, displacement, microrotation, thermal stresses, and carrier density —under arbitrary loading conditions in a two-dimensional half-space domain. The governing equations incorporate micropolar effects, magneto-thermoelastic coupling, and nonlocal constitutive relations, providing a comprehensive description of the system's dynamic behavior. Numerical simulations are performed for a hypothetical magnesium crystal-like material, chosen for its relevance in advanced engineering applications. The results reveal that the inclusion of micropolarity, DPL phase lags, and spatiotemporal nonlocal parameters significantly enhances the accuracy of predicted thermal and mechanical responses, yielding smoother and more damped profiles compared to classical and generalized thermoelasticity models. Graphical representations illustrate finite-speed wave propagation, nonlocal effects, and the influence of phase lag parameters, emphasizing the model's applicability in nanotechnology, microelectronics, and advanced composite design. The present work not only advances the theoretical understanding of micropolar magneto-thermoelasticity but also provides a robust modeling framework for predicting the behavior of micro- and nano-scale systems under complex thermal and magnetic environments. This enhanced predictive capability is crucial for the design and optimization of high-performance materials and devices operating at small scales.

This study examined the nonlinear dynamics of an electrostatically excited microbeam with two thin PZT layers. The design utilized an initially curved microbeam to achieve a wider stable travel range under electrostatic excitation. Analytical model was formulated to optimize the beam’s dimensions and analyze its static and dynamic behavior, such as deflection profiles, resonant frequencies, and vibration responses. The findings reveal several nonlinear effects, including snap-through mechanism, a softening effect near the first natural frequency, and a hardening effect near the third resonance. Additionally, applying a DC voltage to the PZT layers induces an axial force either tensile or compressive based on the voltage polarity that modifies the microbeam’s stiffness. This enables active tuning of the natural frequency and dynamic characteristics.

Topology optimization is a method that achieves optimal structural performance by optimizing material distribution and has been widely applied in fields such as aerospace, automotive manufacturing, and biomedical engineering. Although various methods have been developed to address numerical instability issues in topology optimization, such as checkerboard patterns, gray-scale phenomena, and mesh dependence, effectively selecting an appropriate filtering radius remains a key challenge. To address this, this paper proposes a quantitative method based on gray-scale analysis, conducting frequency domain analysis via 2D discrete Fourier transform (DFT) and combining clustering ratio and clustering index. This method systematically investigates the impact of the filtering radius on numerical instability issues and precisely determines the optimal filtering radius. The effectiveness of the proposed method is validated through numerical experiments, where a comprehensive evaluation index S is defined to determine the optimal filtering radius value under different application scenarios. Unlike traditional empirical rules, the method proposed in this paper improves the precision of filtering radius selection through frequency domain feature analysis, significantly reduces numerical instability, and ensures the accuracy and stability of the optimization results. The research results show that the filtering radius selection method based on gray-scale analysis enhances computational efficiency, optimizes structural performance and manufacturability, and avoids the additional costs that may arise from improper filtering radius selection. This study provides a theoretical foundation and quantitative guidance for the parameter selection of filtering techniques in topology optimization, offering significant engineering application value.

Homogenization-based topology optimization methods used for designing graded lattice structures require multiple scaling laws because of the anisotropic elastic properties of cubic lattice cells. In this study, an isotropy-conditioned density mapping (ICDM) approach is presented to define lattice cells with isotropic elastic properties across the full range of relative densities, enabling the use of a single scaling law in density-based topology optimization. Strut radii for different groups within a cubic lattice cell are determined to satisfy an isotropy condition by evaluating homogenized elastic properties over the entire relative density range required for topology optimization. The resulting isotropy-conditioned lattice cells are used for density mapping in topology optimization based on the solid isotropic material with penalization (SIMP) method. The proposed approach is computationally efficient because it enables macroscopic optimization using the standard SIMP method while ensuring that spatially varying mesoscale lattice configurations satisfy isotropy using a single scaling law. The method is demonstrated through two three-dimensional numerical examples to show its efficacy. The improved structural performance of the optimized designs with the isotropy-conditioned lattice cells is shown by comparing their results with the existing designs.

This work presents an innovative framework for thermoelastic-plastic reliability-based topology optimization, tackling challenges related to material uncertainties, geometric imperfections, and variations in volume fractions. An enhanced Bi-directional Evolutionary Structural Optimization (BESO) method is developed. It integrates thermoelastic-plastic finite element analysis with stochastic reliability constraints to achieve robust and efficient structural designs under combined thermal and mechanical loading. The framework incorporates advanced modeling techniques, including temperature-dependent material properties, elasto-plastic behavior, and eigenmode-based imperfection modeling. A key innovation lies in formulating reliability constraints by treating volume fraction as a random variable to model material usage uncertainty. This ensures compliance with target safety indices. The proposed methodology is verified through detailed numerical examples, including steel beam and shell structures subjected to temperatures up to 800 °C. Results show that the probabilistic designs achieved up to 30% higher load-bearing capacity compared to deterministic ones and demonstrated improved stress distribution and thermal resilience. These enhancements confirm the method’s effectiveness in achieving optimal layouts that balance material efficiency, structural stability, and reliability.

The literature extensively covers functionally graded (FG) composites with individual nanofillers like graphene nanoplatelets (GNP) or multi-walled carbon nanotubes (MWCNT). However, there is a gap in exploring their combined effect on the dynamic response of nanocomposites, which this study addresses. It investigates the impact of GNP flake size on dynamic properties using three commercially available types with flake sizes of 24, 5, and 1.5 μm. The Biot constitutive law is used instead of Hooke’s law to model the polyurethane (PU) foam’s closed-cell structure. The modified Halpin–Tsai model assesses nanocomposite properties, accounting for nanofiller agglomeration. The equations of motion are derived using Hamilton’s principle and the first-order shear deformation theory (FSDT), then solved via the finite element method (FEM). Various parameters, including geometric and porosity parameters, weight fraction, reinforcement patterns, boundary conditions, and rotating velocity, are examined.

In this study, the torsional vibration behavior of functionally graded viscoelastic nanotubes under viscoelastic boundary conditions is investigated in detail within the framework of Doublet Mechanics Theory. A comprehensive solution method is presented that allows the combined consideration of nanoscale effects and viscoelastic behavior; the effects of fundamental parameters such as viscous damping parameter, scale parameter and power law exponent on the system dynamics are analytically revealed. Physical interpretations of both vibration frequencies and damping effects are made from the obtained complex frequency solutions, and the effects of these parameters on the frequency spectrum are analyzed in detail with the help of tables and graphs. The results clearly indicate that classical elastic models are inadequate for the torsional vibration behavior of viscoelastic nanotubes and damping effects at the nano level should not be ignored. Furthermore, it is displayed that there are clear mathematical relationships between the real and imaginary components of the complex frequencies obtained in the system under the direct influence of the viscoelastic model used. In this context, the study makes an important contribution not only theoretically but also in terms of practical applications for the design of nano-mechanical systems.

The current paper investigates the lateral performance of four-layer steel shear walls (SSW) encompassing embedded trapezoidal double-corrugated plates surrounded by flat steel plates. To this end, a one-story and single-span steel frame infilled with four-layer flat-corrugated steel plates, called flat-corrugated steel shear walls (FCSSWs), has been reviewed under lateral loading in the finite element ABAQUS software. Moreover, the lateral performance of flat SSWs (FSSWs), ordinary corrugated steel shear walls (CSSWs), and double-corrugated steel shear walls (DCSSWs) is investigated for comparison. Plate thickness and corrugation angle of the corrugated plates are two parameters. The findings showed that the FCSSWs demonstrate greater maximum strength, energy dissipation, and initial stiffness than other steel shear walls. The difference between the maximum strength of the FCSSWs and FSSWs varies between 6.1% and 13.3%. Also, the initial stiffness of the FCSSWs is at least 16.9% and a maximum of 47.7% more than that of FSSWs. Also, the maximum difference in the highest strength and initial stiffness of FCSSWs with DCSSWs is 16.3% and 12.6%, respectively. The findings showed that FCSSWs have shown increasing load-bearing capacity until the maximum allowable drift angle. CSSWs and DCSSWs may experience strength loss after plate buckling before the ultimate state.

The main goal of this paper is to present the free oscillation, static bending, and buckling of piezoelectric fluid-infiltrated porous metal foam (FPMF) nanosheet resting on Pasternak medium taking into account to flexoelectric and surface elasticity effects. The piezoelectric FPMF nanosheets are rested on Pasternak medium. The nonlocal strain gradient model in conjunction with refined higher-order shear deformation plate theory (rHSDT) and Hamilton’s variational principle derive the motion equations of piezoelectric FPMF nanosheet. The highlights of this study is that the two nonlocal and length-scale coefficients are variable along thickness like material characteristics. The equations of motion were solved through Navier’s method, from which the responses of displacement, stress, natural frequency and critical buckling load were extracted. The accuracy of the proposed method is verified through reliable publications. The outcome of this study reveals the significant effects of the nonlocal and length-scale parameters on the vibration, static bending, and buckling behaviors of piezoelectric FPMF nanosheets. The results of this study are a unique combination of size dependent effects, surface effects and flexoelectric effects, thus it will shed some light on the understanding of electromechanical behaviors at the nanometer scale.