Mechanics of Time-Dependent Materials最新文献

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.