Mechanics of Time-Dependent Materials最新文献

This article explores the memory effects of a three-dimensional cylindrical panel with a void using the Three-Phase-Lag (3PL) theory. The study derives the governing equations for displacement, temperature, void volume fraction, and stress. These equations are solved using Fourier–Laplace transforms and eigenvalue methods. To obtain numerical solutions and generate graphical representations, the transformed equations were inverted. Material properties from Gauthier’s work were used, and graphical results were produced using Mathematica software. The influence of memory response is then demonstrated by comparing kernel functions and time delay parameters within the 3PL porous cylindrical panel. The results show significant changes in the behavior of the panel. The validity of the proposed model is confirmed by comparing its predictions with previously published findings. The authors believe these results can provide valuable insights for various engineering applications involving porous materials. The model allows for accurate prediction of material behavior under different loading conditions, leading to a deeper understanding of various kernel phenomena.

This paper attempts to evaluate the influence of strain rate on the debonding stress of the spherical nanoparticles using a closed form solution. A coherent model to correlate a relationship between the debonding stress of polymer-based nanocomposites and the strain rate was developed. A representative volume element (RVE) containing a spherical nanoparticle, an interphase material, and a pure polymer phase was regarded. A relationship between the debonding stress and the applied strain rate, the material, and geometrical properties of the RVE’s constituents was correlated. In addition to the strain rate, the role of some effective variables such as nanoparticles size, interphase thickness, and interphase stiffness on the debonding stress were investigated. To evaluate the model, three case studies based on the experimental studies performed on silica nanoparticles/epoxy, CaCO₃ nanoparticles/high-density polyethylene (HDPE), silica nanoparticles/photopolymer nanocomposites were conducted. For the nano-silica/epoxy system, the results revealed that by enhancing the strain rate, the normalized debonding stress decreases. Additionally, under a certain strain rate, the normalized debonding stress enhances as much as the stiffness of interphase material increases and the nanoparticle size decreases. In the case of CaCO₃/HDPE nanocomposites, it was observed that by increasing the size of nanoparticles, the normalized debonding stress was reduced significantly. For the nano-silica/photopolymer nanocomposites, it was found that the dependence of the normalized debonding stress on the strain rate is more remarkable for the thicker interphase region. The proposed model can be used to predict the mechanical properties of nanoparticles/polymer systems under high strain rate conditions.

This research formulates a nonlocal systemic model to integrate viscoelastic and thermal deformations in solid structures based on fractional thermo-viscoelasticity theory. This enhanced model offers a more comprehensive understanding by integrating several existing theories. We apply the model to a one-dimensional problem involving a micro-rod made of an electrically conductive polymer, heated by a moving heat source. The analysis employs Laplace transforms with numerical inversion to determine the effects of fractional order, nonlocal elasticity, and nonlocal thermal conduction on thermal dispersion and the thermoviscoelastic response. Comparative figures illustrate the impact of an applied magnetic field. Results show that nonlocal thermal and viscoelastic parameters significantly influence all measured field values, potentially providing guidelines for the design and analysis of thermal-mechanical features in nanoscale devices.

This study investigated the long-term creep behavior of concrete in drilled shafts using conventional and soft-cutting head techniques, focusing on their propensity for internal defects and crack propagation under sustained loading. Triaxial creep tests were performed on concrete specimens subjected to multistage loading to examine the axial- and radial-creep responses associated with each cutting-head method. The findings reveal that concrete prepared with conventional cutting heads exhibits a higher susceptibility to creep failure, attributed to an increased presence of internal defects. In contrast, specimens using soft-cutting heads demonstrated reduced axial- and radial-creep deformations. Concrete cured in laboratory conditions and those cut with soft-cutting heads at various elevations predominantly experienced shearing failures, whereas specimens with soft-cutting heads positioned at higher elevations were more prone to radial tension-shear failures. Considering the Burgers model and fractional-order theory, we introduce a one-dimensional nonlinear damage creep model, alongside a more comprehensive three-dimensional damage creep model. Validation of these models confirms their effectiveness in describing the creep behavior of concrete under different cutting-head disturbances. Importantly, our analysis suggests that the role of soft-cutting head methods on the integrity of cast-in-place concrete piles is comparatively minimal. This insight underscores the potential for optimizing pile-head breaking techniques to mitigate creep-related failures in concrete structures.

Higher reclaimed asphalt pavement (RAP) in asphalt mixtures requires efficient rejuvenation. The efficiency of the rejuvenation can be evaluated by studying the rejuvenator, new and old binder blend. The blend must represent the binder blend inside the asphalt mixture to reflect reality. Extracting and recovering the binder of the rejuvenated asphalt mixtures containing RAP is the best practice to obtain the binder blend inside the asphalt mixture. However, extraction and recovery is not a common practice to study rejuvenation efficiency since it is time-consuming and energy-demanding with exposure to hazardous chemicals. Instead, blending rejuvenator, new binder and the extracted and recovered (E&R) binder from RAP limits the extraction and recovery to the RAP and minimizes efforts for studying rejuvenation efficiency. This study aims to find the blending conditions under which the blend of the rejuvenator, new and RAP binder represents the E&R binder from asphalt mixture concerning rheological performance and behavior properties. The rheological properties of three binder blends prepared under intense, moderate, and low blending conditions were compared with those of the E&R binder. Performance grade (PG), rutting potential (multiple stress creep and recovery test), fatigue resistance (linear amplitude sweep test) and behavioral characteristics (linearity and complex modulus tests) are the rheological properties of this study. It was found that intense and moderate blending conditions are good representatives of the E&R binder with regard to PG and PG+ designation. In addition, intense, moderate, and low blending conditions can be a surrogate for the PAV-aged E&R binder. It can be claimed that any intensity of blending conditions between intense and moderate lead to binder specimen that is almost identical to E&R binder with respect to rutting potential and characterization.

Ultrasonic vibration-assisted grinding (UVAG) enhances surface integrity in machined parts, especially in achieving greater compressive residual stress. Typically, the calculation of residual stresses in UVAG relies on generic finite element software that is not optimized for this purpose, suffering from cumbersome modeling and inefficient calculations. This paper introduces a numerical-analytical hybrid model tailored to predict residual stresses in UVAG. The model independently calculates mechanical and thermal stress fields using contact mechanics and finite difference methods. It employs Hertz’s contact theory and Timoshenko’s thermoelastic theory to establish a correlation between mechanical and thermal loads and the internal stresses in the workpiece. The residual stress field is then determined by considering the thermal-mechanical coupling effects inherent in UVAG. Experiments conducted on 12Cr2Ni4A alloy steel validate the model, with a maximum deviation of 10.5% between predicted and measured residual stresses. Further analysis shows that the presented method has a significant computational efficiency advantage over the simulation method that uses generic finite element software. The work confirms the accuracy and efficiency of the proposed model, offering a novel approach for predicting residual stress in UVAG.

The role of stress-induced diffusion (SID) in influencing the mechanical response and diffusion of Li in viscoelastic electrode particles of Lithium-ion batteries is studied. A two-way coupled chemo-viscoelastic model is developed for this purpose, and the governing equations are solved via the finite element method using deal. ii, an open source C++ library. Comparative studies between one-way and two-way coupled chemo-viscoelastic models reveal that concentration and stress are initially larger for the two-way coupled model, but later they reduce in magnitude compared to the one-way coupled model. The level of filling at which the switch is observed decreases with increase in particle size. The switch occurs due to change in the sign of gradient of hydrostatic stress for a viscoelastic material from negative to positive and its concurrent effect on diffusive flux as a result of two-way coupling between stress and diffusion. Further, from comparative studies between two-way coupled elastic and viscoelastic models, it is observed that speed of filling is greater for an elastic particle in comparison to a viscoelastic particle, and the gap increases when the particle size is smaller. In addition, lower values of stresses are observed for viscoelastic electrode particles, and the difference between maximum stress generated increases with increase in particle size. Thus, the time scales associated with viscoelastic constitutive response and diffusion process alters the SID effects and could be tuned while designing electrodes to mitigate slowing down of diffusion and fracture.

This paper introduces a fractional-order model integrated with a damage variable to effectively characterize the stress or strain responses under strain- or stress-controlled cyclic loading. We derive a relationship among mean stress, ratcheting strain, and cyclic number from the established fractional constitutive relationship. Experimental validation with polymeric data demonstrates the validity of our model, indicating how fractional order captures the effects of various loading conditions—including mean stress, temperature, and loading rate—on ratcheting strain responses. Additionally, our model offers a simpler mathematical framework than the existing models, without compromising accuracy.

This research investigates the effects of multi-slip conditions and entropy production on the flow of viscoelastic (Jeffrey) nanofluids in asymmetric channels, to determine the implications for healthcare applications such as cryopreservation and therapeutic thermal devices. By employing numerical simulations via the Shooting method and NDSolve tool, we examine the influence of motile microorganisms on the fluid’s thermal and entropic characteristics. Our findings, illustrated through graphical analysis, demonstrate that optimizing thermal slip and minimizing viscous slip can significantly reduce entropy generation. Additionally, we observe that the thermal profiles are affected by the Brinkman number-diminishing in size, yet expanding due to the Jeffrey fluid’s properties. This investigation not only advances our understanding of microbe motion in physiological fluids but also opens directions for developing precise therapeutic and diagnostic tools for microbial infections and related disorders.