Mechanics of Time-Dependent Materials最新文献

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.

Pressure tubes (PTs) play an important role in the safe and efficient operation of Nuclear Power Plants (NPPs) as they contain the fuel bundles and provide structural integrity. Creep has been identified as one of the main degradation mechanisms of PTs, which are made widely of Zr-Nb alloys. The creep curve of a material gives an insight into the nature of its creep behavior. In the present investigation, accelerated creep experiments were conducted on Zr-2.5Nb PT alloy in the stress and temperature range of 22–58 MPa and 600–850 °C, respectively. Two data-driven models, namely Radial Basis Function Neural Network (RBFNN) and Least Square Fit (LSF) were developed to simulate the non-linearity of the creep curves. Applied stress, test temperature, and time to failure were taken as the input parameters for the models. It was observed that although the LSF could predict the primary creep zone, it failed to predict the transition between the secondary and tertiary creep region. However, the creep curves predicted by the RBFNN model were in close agreement with the experimental results, having a confidence level of ≈ 0.99. Two separate sets of creep experiments were also done later to verify the accuracy of the proposed models. The results from the study established the ability of the RBFNN technique to simulate the complex behavior of the creep curves.

The present article addresses a novel mathematical model involving the Atangana-Baleanu (A-B) definition of fractional derivatives in time that offers a new interpretation of the thermo-mechanical effects inside skin tissue during thermal therapy. A Laplace transform mechanism is proposed to achieve closed-form solutions for prominent physical quantities, such as temperature, displacement, strain, and thermal stress. Computational results are obtained in time domains using an efficient numerical inversion algorithm of Laplace transform. The impact of the fractional parameter is investigated on the variations of the field quantities through the graphical results. The behavior of each physical field is speculated against the time parameter. The domain of influence of each field quantity is suppressed when the definition of the Atangana Baleanu fractional model is adopted, replicating that the waves under the A-B fractional model predict the finite nature of propagation compared to the conventional heat transport model. Further, we observe that the nature of the thermo-mechanical waves becomes stable earlier inside the tissue.

This research investigates the impact of thermoelastic coupling on thermally conducting, homogeneous, and isotropic Kelvin–Voigt-type circular microplate resonators. The study utilizes the Moore–Gibson–Thompson technique, which incorporates viscous effects. We examine the use of clamped boundary conditions and obtain analytical solutions in the Laplace-transform domain. In order to clarify the thermomechanical effects on the vibrations of a ceramic Si₃N₄ plate resonator, we calculate numerical outcomes in the time domain by employing the inverse Laplace transform. We examine the impact of viscosity on many physical phenomena, including deflection, temperature, displacement, thermal moment in the radial direction, and radial stress. We give graphical findings that compare the results with and without the presence of viscosity. The study evaluates the precision and feasibility of the MGTE thermal-conductivity theory by comparing its numerical outcomes with well-established thermoelastic models, such as the classical theory, Lord–Shulman theory, and Green–Naghdi II and III theories. The MGTE theory showcases improved accuracy, facilitating the production of circular micro/nanoplate resonators with exceptional quality and decreased energy dissipation.