Mechanics of Time-Dependent Materials最新文献

Many industrial processes contain the utilization of nanoparticles to improve the thermal performance of the physical systems. This research discusses the utilization of nanoparticles and thermal transport phenomenon in a stretched cylinder. The contribution of convective boundary constraints and thermal radiation is taken in heat transfer-modeled equations with an external heating source. The flow-modeled equations have been derived in Cartesian coordinates in the rotating frame. The set of nonlinear-coupled PDEs (partial differential equations) are obtained for the considered model in the simplified form by engaging boundary layer theory. Afterward, a set of ODEs (ordinary differential equations) was obtained by utilization of similarity transformation. The modeled equations are dealt with numerically via the finite element approach. The solution is displayed graphically against different emerging parameters. It is recorded that the production of the entropy mechanism generated by tetra-hybrid nanofluid is higher than the production of the entropy mechanism generated by ternary hybrid nanofluid.

The current study investigates the linear viscoelastic response of emulsified-asphalt cold recycled mixtures (ECRM), incorporating reclaimed asphalt pavement (RAP), fresh aggregates, cement, water, and bituminous emulsion. Specifically, two types of ECRM are analyzed: a conventional mixture with 100% RAP (ECRM1) and a modified version with 75% RAP activated by heating (ECRM2). The research highlights the distinct mechanical response resulting from variations in production processes and the RAP content of the mixtures. The study examines the rate-dependent responses under various confinement conditions, temperatures, and frequencies through repeated haversine compression loading. Further, a novel approach to determine the reference temperature is proposed, and master curves are constructed using the generalized sigmoidal and Huet–Sayegh models. Even though ECRM1 and ECRM2 have different RAP content, production processes, and volumetric properties, the differences between the mixtures using the dynamic modulus and storage-modulus master curves are not substantial. However, the loss-modulus master curve distinctly captures the differences between the mixtures, with ECRM1 exhibiting a higher loss modulus due to its higher effective binder content. Moreover, the relaxation spectrum also captures the distinct response between the materials, mirroring the response seen in the loss modulus. It is also observed that confinement pressure significantly influences the dynamic modulus and storage modulus of ECRMs at low reduced frequencies. However, the influence of confinement pressure on the loss-modulus master curve and relaxation spectrum is negligible. This indicates that confinement pressure only influences the real part of the complex modulus, with no effect on the imaginary part.

Structures made of graded composites play an important role in various industrial fields, such as aerospace and biomechanics. By incorporating nonlocal stress theory the internal length scale parameter of the nonlocal model provides detailed information on long-range forces of atoms or molecules. This paper investigates the size-dependent modeling of a functionally graded unbounded medium influenced by a heat source and an induced magnetic field on the bounding plane. The heat transport equation is governed by a unified formulation that integrates both the three-phase-lag model and Moore–Gibson–Thompson theory of generalized thermoelasticity, incorporating a memory-dependent derivative with nonlinear and linear kernels. Using nonlocal stress theory, the constitutive equations are addressed. The basic equations are simplified in the transformed domain through the Laplace and Fourier integral transforms. To obtain solutions in the real space-time domain, the Fourier transforms are analytically inverted using residue calculus, with poles of the integrand numerically determined in the complex domain via Laguerre’s method. Subsequently, the numerical inversion of the Laplace transform is performed using a method based on Fourier series expansion. The computational results and corresponding graphical representations reveal significant effects of parameters such as the nonlocality parameter, time-delay parameter, and the influence of the magnetic field. Furthermore, the impact of different kernel functions is examined, demonstrating the superiority of nonlinear kernels over linear kernels within this new theoretical framework.

This article uses a memory-dependent derivative (MDD) — which may be better than a fractional derivative — to develop a novel heat conduction problem in a functionally graded material (FGM) layer with a distinct exponential gradient model. A theoretical framework is designed for a functionally graded plate (FGP) incorporating the fractional heat conduction theory that incorporates single-phase-lag (SPL) and two-temperature discrepancy factors to capture the thermoelastic response and the memory-dependent effect. Then, the modified model is used to investigate the thermoelastic response of an FGP subjected to thermal shock at the left surface of the plate, keeping other faces at zero temperature. The temperature change is determined using the integral transform technique, and the solution is obtained in the Laplace transform domain. The transient temperature response in the time domain is evaluated through numerical inversion of the Laplace transform to generate numerical data. The general solutions of the governing equation of stress function are obtained by utilizing material attributes represented by the exponential-law index. The transient responses, namely temperature, displacement, and stress, are graphically depicted. FGP is composed of partially stabilized zirconia (PSZ) particles, and the austenitic stainless steel (SUS304) matrix was used in the analysis. The use of FGM requires careful compositional choices to prevent thermal stresses from being generated in the FGP. The study compares temperature distributions using non-Fourier and classical Fourier models, revealing wave-like phenomena in fractional heat transfer, which are undetected in classical Fourier heat conduction.

To conduct a more realistic numerical simulation analysis of jointed rock mass engineering in cold regions, shear creep tests were conducted on the jointed rock masses under freeze-thaw and chemical corrosion. Based on test results, a shear creep damage model of jointed rock masses was established. The FISH language was used on the 3DEC platform to implement the secondary development of the model, and the rationality of the model was verified through degradation analysis and test data. Finally, the developed model was used to numerically calculate the creep characteristics of tunnel in cold regions, the research results show that: (1) The maximum creep deformations of tunnel subjected to 0, 20, 40, and 60 freeze-thaw cycles and chemical corrosion are 16.0 mm, 20.9 mm, 24.2 mm, and 34.1 mm, respectively. With the increase of freeze-thaw cycles and chemical corrosion, the creep deformation and plastic zone gradually increase. (2) As the joint plane inclination angle increases from 0° to 90°, the creep deformation gradually decreases. When the joint plane inclination angle are 0°, 30°, 60°, and 90°, the maximum creep deformations are 29.7 mm, 27.6 mm, 24.2 mm, and 22.5 mm, respectively. (3) With the increase of creep time, the creep deformation of the tunnel gradually increases. The arch deformation is 9.3 mm, 18.6 mm, 24.2 mm and 27.3 mm after 10 days, 30 days, 60 days and 90 days respectively. The research results provide an effective computational method for the stability analysis of rock mass engineering in cold regions.

To reveal the bedding effects on the deformation field evolution of coal bodies containing parallel bedding under static loading, the maximum shear strain field of raw coal specimens under vertical bedding loading and parallel bedding loading conditions was observed by the digital scatter correlation method, and the deformation field evolution and deformation localization characteristics of raw coal specimens containing parallel bedding during loading process under two loading conditions were quantitatively analyzed. A damage variable was defined to describe the damage of coal specimens based on the characteristic statistics, and a damage constitutive model was established to reflect the full stress–strain characteristics of coal specimens with parallel bedding. The results show that the strain field of the parallel-bedding-loaded specimens is patchily distributed during the initial compaction stage, whereas the vertical-bedding-loaded specimens form a deformation-concentrated area at the loading end. Before and after the peak strength, the strain field of the vertical-bedding loading specimen changes dramatically, and the specimen shows shear damage, whereas the strain field of the parallel-bedding loading specimen does not have large changes, and the specimen shows splitting damage, with higher crack development and degree of specimen failure. The initiation stress of deformation localization in the vertical bedding specimens is closer to the peak strength, whereas the parallel bedding specimens are more likely to show deformation localization characteristics. The damage constitutive model based on the characteristic statistics can well reflect the stress–strain characteristics of the raw coal specimens under the loading conditions of vertical and parallel bedding.

In present work, Green–Nagdhi (type III) thermoelastic half-space under hydrostatic initial stress is taken into consideration. The thermoelastic half-space is subjected to a mechanical load acting on the free surface along the normal direction. The thermal conductivity of the medium is believed to be temperature-dependent and to vary linearly. The formulas for the temperature distribution, stress, and displacement components are obtained by applying the normal mode analysis approach. Analytical evaluation is performed on the physical characteristics exhibiting temperature-dependent thermal conductivity. The influence of temperature dependency and hydrostatic starting stress on these physical parameters is then illustrated graphically by evaluating these physical values numerically using algorithms created in MATLAB 7.0.