Continuum Mechanics and Thermodynamics最新文献

This research presents an innovative spatiotemporal nonlocal model designed to analyze the behavior of a thermoelastic micropolar medium under laser irradiation. The model incorporates phase-delay heat conduction theory, enabling a more accurate depiction of thermal and mechanical responses, particularly in nanoscale materials. By accounting for both spatial and temporal nonlocal interactions, the model effectively addresses size-dependent phenomena, which are essential for understanding the behavior of micropolar materials. These nonlocal effects consider how the surrounding environment and the material’s previous responses influence its current behavior, thereby enhancing the model’s precision and real-world relevance. The integration of phase-delay theory facilitates the characterization of non-Fourier heat conduction, which is critical for accurately modeling material behavior under brief laser pulses. Moreover, the phase delays capture the time-lagged responses of materials to sudden thermal inputs, a vital consideration in applications involving laser heating. The study includes graphical representations that illustrate the impact of key parameters, such as micropolarity, phase delay, and the nonlocal index, on the material’s mechanical behavior with respect to distance. This analysis enhances understanding of spatial variations in stresses, displacements, and mechanical properties of micropolar elastic materials under laser heating.

Thermal shock testing is a crucial method for evaluating the quality and lifespan of thermal barrier coatings, which are widely used in the aerospace and power generation industries. Currently, these tests are predominantly conducted under static conditions, which do not fully replicate real operational environments. In this study, we aimed to assess the strength and quality of thermal barrier coatings under dynamic conditions and to collect data on temperature distribution, supported by experimental analyses. To achieve this, a specialized test setup was designed, coating applications were performed, and lifetime tests were conducted. In addition to the test results microscopic examinations of the coatings were performed. The findings reveal that static tests do not accurately reflect the effects observed under dynamic operating conditions. Furthermore, the damage occurred significantly faster in the dynamic tests than in the static tests. These results highlight the necessity of dynamic testing for a more reliable assessment of thermal barrier coatings.

This work presents a comprehensive theoretical framework for flexoelectric materials by incorporating higher-order strain gradient and polarization gradient effects into the constitutive modeling. Using an extended strain gradient elasticity (SGE) approach, coupled with a generalized Toupin-like variational formulation, we derive governing equations, balance laws, and boundary conditions based on an enriched internal energy density function. Analytical solutions, expressed in terms of modified Bessel functions, provide key insights into the role of higher-order gradients in influencing displacement, polarization, and electric fields. The study highlights the critical impact of size effects on flexoelectric response, revealing that reducing material thickness enhances sensitivity and energy conversion efficiency. Furthermore, numerical simulations validate the theoretical model and demonstrate its applicability in the design of nanoscale flexoelectric sensors and energy harvesters. These findings establish a robust theoretical foundation for optimizing nanoscale electromechanical devices, with potential applications in biomedical sensors, structural health monitoring, and energy-efficient electronics.

This innovative study presents a novel framework for analyzing the axial dynamic response of a rotating thermoelastic nanobeam subjected to a moving load, marking a significant advancement in the field of nanoscale mechanics. By integrating the Klein-Gordon nonlocal theory with an innovative internal time scale parameter, the research derives governing equations that effectively capture nonlocal effects. The application of Hamilton’s principle in conjunction with Euler-Bernoulli beam theory ensures precise modeling, while the dual-phase lag (DPL) framework accounts for thermoelastic properties without energy dissipation, incorporating both internal length and time scale parameters. The use of the Laplace transform method to solve the resulting partial differential equations demonstrates a robust analytical approach. A detailed numerical example highlights the effects of nonlocal parameters, rotation, and load speed on axial dynamic deflection, stress, and temperature distribution, with graphical results validating the model’s accuracy against previous studies. This study sets a new standard for modeling complex nanoscale systems and provides valuable insights into their dynamic behavior.

The current technological development has put forward higher requirements for the multifunctionality of materials and structures. This study delves into the bandgap attributes of a zigzag connection (ZC) lattice metamaterial, capable of being constructed through the mirroring or rotation of basic units. This metamaterial exhibits nearly zero thermal stress when subjected to thermal expansion deformation. Through a comprehensive analysis and comparison of three distinct arrangements, the rotational symmetrical quadruple cell emerges as the optimal choice. Subsequently, the investigation explores the influence of various geometric dimensions, constituent materials, and additional parameters on the bandgap. The findings elucidate the exceptional bandgap characteristics of this configuration, coupled with its ability to accommodate tailored thermal expansion coefficients and minimize thermal stress. By judiciously selecting materials and refining structural design, the study envisages the attainment of multiple objectives in thermal expansion properties and bandgap modulation. Such endeavors hold promise for enhancing the tunability and multifunctionality of the metamaterial, thereby advancing its utility across diverse applications.

This study presents a generalized photo-thermoelastic model for solid semiconductor media subjected to photoacoustic excitation within the framework of multi-temperature theory. The model captures the complex interactions among optical, thermal, and elastic waves, offering a more realistic representation compared to traditional single-temperature approaches. The governing equations are formulated by coupling the photoacoustic source with multi-temperature thermoelasticity, accounting for separate thermal responses associated with thermodynamic and conductive temperature fields. Analytical solutions are obtained using the normal mode analysis technique, allowing for detailed evaluation of the main physical field distributions. Comparative simulations highlight the differences in wave behavior under multi-temperature theories. The results show that the hyperbolic and two-temperature models outperform classical models in capturing sharp thermal gradients, delayed thermal wavefronts, and stronger stress and displacement responses. These findings confirm the importance of advanced thermal theories in improving the design and reliability of semiconductor-based photonic and optoelectronic devices.

In this paper, a one-dimensional Timoshenko-like equivalent beam model, embedded in a 2D space, is developed to analyze the static response of a chiral metamaterial, first presented in Misra et al. (Contin Mech Thermodyn 32:1497–1513, 2020). This is a beam-like structure, here referred to as the ‘grain beam’, which is made of a periodic assembly of a grain-pair interconnected with solid bars, exhibiting chirality through shear and axial strains coupling. The derivation of the beam model is conducted within the framework of the direct one-dimensional approach, wherein the constitutive law is established through a suitable homogenization procedure, that relies on an energy equivalence between a cell of the periodic model and a segment of the solid beam. Based on the geometry of the interconnecting elements of a grain-pair of the microstructure, analytical as well as numerical approaches are developed to identify the constitutive parameters, the latter grounded on a FE analysis of the cell. The analytical identification procedure, which shed the light on the dependence of the elastic coefficients upon proper defined nondimensional parameters, as the cell aspect ratio and the slenderness of horizontal and vertical fibers, is shown to be effective in designing grain beams with targeted stiffnesses, chirality and macroscopic behavior. The linear static response of some grain beams, taken as case studies, is analyzed and the results obtained by the Timoshenko-like beam model and the FE analyses, these latter carried out on refined models of grain beams, are compared. The effectiveness of the beam model, its limits of applicability, and the associated error magnitude in describing the static behavior of grain beams are investigated and discussed.

This study examines the two-dimensional deformation of a functionally graded Green Naghdi (type-III) thermoelastic half-space under hydrostatic initial stress. The material properties of the medium are assumed to vary along two directions. Such type of problem has not been attempted earlier. Using the normal mode technique, analytical expressions for displacement components, temperature distribution, and force stress are derived. The numerical evaluation of these field variables reveals the impact of initial stress and material inhomogeneity on thermoelastic behavior. Graphical representations illustrate the variations in displacement and stress fields, emphasizing the intricate interplay between mechanical and thermal responses. These findings provide valuable insights for stress-strain analysis and the design of advanced engineering materials in thermoelastic applications.

The paper studies the problem of wave propagation through a multi-layered structure, which consists of a finite number of solid / fluid parallel layers of finite thickness. By considering the structure as a protective multi-layered barrier placed in a (scalar) fluid space to reduce the amplitude of the plane incident wave, we give an exact explicit analytical representation for the transmission coefficient, in the case of arbitrary finite number of layers and arbitrary values of their thicknesses. We demonstrate wave properties of the barrier for various types of the geometry, including the case of ultra-low frequencies.

This paper presents a theoretical investigation of a functionally graded hydro-poroelastic semiconductor material subjected to photo-thermoelasticity theory. The material properties, including thermal conductivity, elasticity, and porosity, are assumed to vary spatially following a functionally graded distribution. A one-dimensional problem is formulated to analyze the coupled interactions between the hydro-semiconductor medium’s thermal, mechanical, and electronic transport phenomena. The governing equations incorporate hydrodynamic effects, poroelasticity, and semiconductor carrier transport under the influence of thermal and photonic excitation. The Laplace transform technique is employed to obtain analytical solutions in main physical fields. Numerical results are derived using inverse Laplace transformation, and the effects of functionally graded parameters on wave propagation and heat transport are examined. Graphical analysis illustrates the impact of grading index and porosity on the material’s response. The results highlight the significance of functional grading in tailoring the behavior of hydro-poroelastic semiconductors for advanced technological applications, including optoelectronic devices, photodetectors, and thermal management systems.