Taking into account the universal dependence of the viscosity of a boundary lubricant on temperature and strain rate to describe stop-start experiments

The tribological system consisting of two blocks with atomically smooth surfaces separated by a boundary lubricant layer is considered. A spring the free end of which is driven is attached to one of the blocks. A thermodynamic model is used to study the influence of the universal relationship between the viscosity of a non-Newtonian lubricant and temperature and strain rate on friction modes. The melting and solidification of the lubricant layer are taken to be second-order phase transformations. The specific features of widely used stop-start experiments, where a system stops for a certain time and then resumes its motion, are analyzed. The influence of the temperature, the shear velocity, and the external load on the behavior of the system is investigated. The conditions of transitions between the fluid (sliding), stick-slip, and dry friction modes are determined for the lubricants consisting of linear alkanes of various lengths.