The Nishihara creep model is an extremely effective method in the field of sandstone creep model research. However, the Nishihara creep model curve for sandstone under the marine environment (the coupled effect of chemical corrosion and temperature) does not fit the actual creep test data well. Based on the Nishihara creep model, we discovered that, on the one hand, the viscoelastic elements in the Nishihara model are replaced by the viscoelastic elements containing temperature and pH factors, which can accurately describe the influence of temperature and pH on rock creep characteristics; on the other hand, the viscoplastic elements in the Nishihara model are replaced by nonlinear viscoplastic elements, which can accurately describe the accelerated creep stage of the rock mass. After modifying Nishihara’s creep model twice, a new temperature–pH damage nonlinear creep model is established. The creep curve of the temperature–pH damage nonlinear creep model is compared with the creep test data of sandstone. The comparison results indicate that the creep curve of the nonlinear creep model has a high degree of fit with the creep test data of sandstone (accuracy > 92%). This validates the correctness of the newly established temperature–pH damage nonlinear creep model presented in this paper, demonstrating that the new model can effectively reflect the influence of temperature and pH on the creep characteristics of sandstone.

The tripod sliding universal coupling (TSUC) is a novel type of coupling developed through independent research. This study theoretically investigates the effects of the grease flow index and initial viscosity on thermal elastohydrodynamic lubrication (TEHL) properties. Three common grease formulations were evaluated for TSUC lubrication. The numerical results yielded the following insights: a larger flow index increases film thickness and elevates the secondary pressure peak. A higher initial viscosity enhances film thickness yet significantly elevates the temperature distribution due to quadratic growth in viscous dissipation. It also intensifies the secondary pressure peak, which may exceed the central Hertzian pressure under heavy loads, thereby accelerating surface fatigue. The lubrication performance varies significantly across grease types. When pressure–viscosity coefficients and densities are similar, the initial viscosity becomes the dominant factor. These findings provide a theoretical basis for optimizing grease selection in TSUC systems to improve the efficiency and durability of lubrication.