Shear rate and pressure effects on boundary slippage in highly stressed contacts

Boundary slippage has been well confirmed using micro/nano measuring technologies and molecular-dynamic simulations. However, the characteristics of slip behaviour are still open for discussion due to their various behaviors under different conditions. This paper focuses on the boundary slippage under EHL conditions and its dependence on the shear rate and pressure. By tracing the movement of entrapped high molecular polymeric lubricants, boundary slippage was inferred. The slip length was measured under different conditions. The results showed that slip length varies exponentially with shear rate, indicting a nonlinear relationship. With pressure increasing, the slip length increased linearly in double logarithmic coordinates.

► Boundary slippage is observed and quantified under high pressure conditions.
► The slip length was found a strong function of shear rate under high pressures.
► Slippage on the steel surface may inspire the measurement of oil rheology properties.