Mechanics of Time-Dependent Materials最新文献

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.

Hybrid nanofluids, which incorporate two distinct nanoparticles, are an innovative class of nanofluids designed to improve thermal and mechanical properties. These fluids have garnered considerable interest in numerous engineering and scientific fields. The fundamental goal of this research is to investigate the heat-transfer increase of MnZnFe₂O₄-NiZnFe₂O₄/C₁₀H₂₂ hybrid nanofluids in the presence of magnetohydrodynamics, nonlinear thermal radiation, and the Biot number on a stretched sheet. In this case, nanomaterials (MnZnFe₂O₄ and NiZnFe₂O₄) are combined with a base fluid C₁₀H₂₂. To do this, the system’s partial differential equations are transformed into a set of nonlinear ordinary differential equations using systematic similarity transformations. The shooting approach is then used in combination with MATLAB’s BVP4C solver to solve the resultant ordinary differential equations. The study presents the impact of various physical parameters, including the porosity parameter, magnetic parameter, Prandtl number, thermal-radiation parameter, Biot number, and Schmidt number, on the velocity and temperature fields, illustrated through graphs and tables. The velocity field reduces for increasing values of both magnetic and porosity parameters. The thermal-distribution profile is increased for increasing variations of the temperature-ratio parameter, Biot number, volume fraction of nanoparticles, and the thermal-radiation parameter. The MnZnFe₂O₄-NiZnFe₂O₄/C₁₀H₂₂ hybrid nanofluids combine thermal, magnetic, and fluidic properties, making them versatile for applications in thermal management, medicine, industrial processes, environmental remediation, and advanced sensing technologies. Their multifunctional characteristics provide significant advantages in improving efficiency, performance, and control in various engineering and scientific fields. This research has potential applications in heat transfer, biomedical research, manufacturing, aerospace technology, and beyond.

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.

The present study explores generalized thermoelastic diffusion within the framework of refined four-phase lag models for an isotropic unbounded medium containing a cylindrical cavity, considering traction-free boundaries and heat sources that vary harmonically. Employing Laplace transform and later using the eigenvalue approach, we find the analytical formulations for various thermo-physical quantities in the transformed domain. Lastly, the Riemann-sum approximation method is employed to obtain the solutions in the real-time domain. We thoroughly examined the sensitivity of the various physical parameters across all investigated domain, and the findings are illustrated both graphically and in tabular formats.

Recycling agents (RAs) are additives incorporated into recycled asphalt mixtures to mitigate the negative effects of using recycled asphalt materials on the performance. This study evaluates the impact of RAs on long-term aging susceptibility and performance at two scales. At the binder scale, rheological tests are conducted on recycled binder blends to examine the effects of RAs on high- and intermediate-temperature rheological behavior. At the mixture scale, dynamic modulus, cyclic-fatigue tests, and Hamburg Wheel Tracking Tests (HWT) are employed to assess the effects of RAs on linear viscoelastic properties, cracking resistance, and rutting resistance, respectively. In addition, changes in binder and mixture properties with long-term aging are assessed. In both binder and mixture analyses, the RA-modified systems are compared to ‘reference’ systems that reflect the current practice in the state from which the mixtures were sourced. The results indicate that RA-modified binders exhibit somewhat poorer rutting performance compared to the reference systems while the HWT test shows that all systems fulfilled the minimum mixture rutting criterion proposed by NCHRP Project 09-58. The addition of the RAs to asphalt binder yielded decreases in dynamic shear modulus and increases in phase angle compared to the reference systems in all cases. However, the rheological effects of the RAs diminished at the harshest long-term age level considered at both the binder and mixture scales. The cyclic-fatigue performance of mixtures prepared with the RAs were similar to the reference systems at the long-term age level evaluated.

Coal, as a complex gas-bearing medium, exhibits unique rheological behavior under mining disturbance. However, with increasing mining depth, the creep and seepage mechanisms of low permeability coal remain unclear. Therefore, to investigate the coupled relationship between creep and gas seepage in low permeability coal, time-dependent triaxial experiments were conducted in this study. To consider the effects of gas, a modified creep model based on the Nishihara creep model was developed and validated by numerical simulations and experimental results. The correlation between coal creep and seepage was then analyzed under different gas pressure conditions, showing a significant reduction in Young’s modulus during creep. This reduction indicates a strong correlation between creep and gas seepage, which is supported by the agreement between creep strain and permeability curves. In addition, the results show a significant attenuation effect in the seepage process at different gas pressures due to pore pressure and adsorption. It is worth noting that unlike conventional soft coal, no permeability reduction was observed in the initial stage due to the low permeability and stiffness of the coal. And it was shown that the presence of methane accelerated the creep behavior of the coal, resulting in a decrease in permeability. Overall, this study provides important insights into the rheological behavior of low-permeability coal under mining disturbance and sheds light on the mechanisms governing gas seepage in coal.