In this paper, we investigate the thermal friction sliding contact of a functionally graded piezoelectric material (FGPM)-coated half-plane subjected to a rigid conductive cylindrical punch. This study considers the effect of the thermal convection term in heat conduction. The thermo-electro-elastic material parameters of the coating vary exponentially along its thickness direction. Utilizing thermoelastic theory and Fourier integral transforms, the problem is formulated into Cauchy singular integral equations of the first and second kinds with surface stress, contact width, and electric displacement as the unknown variables. The numerical solutions for the contact stress, electric displacement, and temperature field of the graded coating surface are obtained using the least-squares method and iterative techniques. It can be observed that the thermo-electro-elastic contact behavior of the coating surface undergoes significant changes as the graded index varies from −0.5 to 0.5, the friction coefficient ranges from 0.1 to 0.5, and the sliding velocity changes from 0.01 m/s to 0.05 m/s. The results indicate that adjusting the graded index of the coating, the sliding speed of the punch, and the friction coefficient can improve the thermo-electro-elastic contact damage of the material’s surface.

To explore the effect of storage conditions on the freshness of fishmeal, the acid value (AV), volatile basic nitrogen (VBN), and pH value were used as freshness evaluation indexes to explore the changes in freshness during storage and the influence of mold count on these indexes. The effects of storage temperature and relative humidity (RH) on AV, VBN, pH value, and mold count were studied using a single-factor test, and grey relation analysis (GRA) was used to assess the association between mold count and freshness indexes. The appropriate storage conditions were determined using the technique for order preference by similarity to ideal solution (TOPSIS) method, which provides theoretical support for fishmeal storage. The results showed that the AV increased during the storage of fishmeal, while the VBN and pH value decreased; the pH value tended to be stable in the later storage stage. The VBN and pH values could not be used as evaluation indexes in the early stage of deterioration. Higher storage temperature was conducive to the storage of fishmeal, but higher RH was not. The results of the GRA showed that the mold count was correlated with each freshness index. The correlation between mold count and VBN was the largest, followed by AV, and the correlation with pH value was the smallest. The TOPSIS method finally determined the suitable storage conditions for fishmeal to be around 25 °C for storage temperature and 60% for RH. The results serve as a future reference for the storage of fishmeal.

This study investigates the thermoelastic frictional contact and wear behavior during reciprocating sliding of a conductive cylindrical punch on a functionally graded piezoelectric material (FGPM)-coated half-plane. The thermo-electro-elastic properties of the coating vary continuously along the thickness direction according to arbitrary gradient functions, with thermal parameters being temperature-dependence. A theoretical framework for the coupled thermo-electro-elastic frictional contact problem is developed and solved using the finite element method. A sequential coupling approach is employed to integrate thermoelastic frictional contact with piezoelectric effects. Furthermore, wear on the coating surface is modeled using an improved Archard formulation, accounting for its impact on thermal sliding frictional contact characteristics. Numerical simulations examine the influence of wear, cycle number, friction coefficient, gradient index and gradient form on the coupled thermo-electro-elastic response of the FGPM coating structure. The numerical results demonstrate the gradient index and gradient form can effectively mitigate thermo-electrical contact-induced damage and reduce friction and wear in piezoelectric materials.

To address the issues of local high temperatures, thermal stress concentration, and the susceptibility to spalling of homogeneous ceramic coatings in disc brakes under high-frequency thermal–mechanical cyclic loading, this paper proposes a surface design scheme incorporating a functionally graded material (FGM) coating along the thickness direction. A three-dimensional thermal frictional contact model of a graded coated brake disc with continuously varying material properties (silicon carbide/gray cast iron) along the thickness direction is established by developing user subroutines on the Abaqus finite element platform. The effects of exponential, power-law, and trigonometric gradient distributions on the transient temperature and stress fields are systematically compared. The results indicate that the high thermal conductivity silicon carbide coating significantly reduces the disc surface temperature; however, a homogeneous coating induces interfacial thermal stress concentration due to a sudden stiffness mismatch. The graded design effectively mitigates the stress concentration through a smooth transition of material properties. Taking the power-law function (n = 1.5) as an example, this design not only significantly reduces the maximum disc surface temperature but also limits the residual equivalent stress at the end of braking to 245 MPa, which is approximately 24.8% lower than that of the homogeneous coating (325.8 MPa). The study demonstrates that the gradient function exerts a stronger regulatory effect on the stress field than on the temperature field, meaning the two cannot be simultaneously optimized. Nevertheless, exponential functions and power-law functions with small exponents can achieve a favorable balance of thermal–mechanical performance. This research reveals the mechanism by which thickness-direction gradient distributions regulate thermal–mechanical coupling behavior, providing a theoretical basis for the gradient design of thermal fatigue-resistant friction components.

This paper investigates two axisymmetric thermoelastic contact problems of functionally graded materials (FGMs) with arbitrarily varying material properties. A rigid, insulated spherical punch slides/rotates on the surface of the FGM coating at a constant velocity. The primary novelty of this study lies in developing a comprehensive semi-analytical framework capable of evaluating the complex thermoelastic behaviors of FGM coatings with arbitrarily varying properties under both sliding and rotating frictional heating conditions. It is assumed that there is no coupling between the tangential stress and the normal stress, but the tangential stress on the surface cannot be ignored. The frictional heating is generated in the contact region by a sliding/rotating spherical punch. A homogeneous multi-layered model is employed to simulate the thermoelastic properties of FGM coatings. By making use of the transfer matrix method and the Hankel integral transform, the two axisymmetric thermoelastic problems are reduced to Cauchy singular integral equations, which are then numerically solved to obtain the normal contact stress, radial stress and surface temperature. The key findings demonstrate that (1) tailoring the coating gradient index and gradient type can effectively mitigate thermal stress concentrations under these frictional heating modes; (2) higher sliding or angular velocities significantly amplify the thermoelastic effects, leading to elevated surface temperatures and radial tensile stresses; and (3) the proposed arbitrary gradient model provides a more flexible and accurate tool for optimizing FGM coatings against surface failure in extreme thermal-mechanical environments.