Strain rate effect on frictional behaviour of Hardox 450 steel

Abstract The influence of strain rate on the frictional behaviour of high-strength Hardox 450 steel have been investigated using both experimental and numerical approaches. The ring compression test method was employed to identify the friction coefficient across a wide range of strain rates, from quasi-static (0.005 s -1 ) to dynamic conditions (3 000 s -1 ) utilizing a split Hopkinson pressure bar test. Tests were conducted under dry conditions and with MoS 2 grease lubrication. The results demonstrate a significant decrease in the friction coefficient with increasing strain rate; for dry friction, the value dropped from 0.176 to 0.015. It was observed that at high strain rates (1 000 s -1 ), the friction coefficients for both dry and lubricated conditions converge, suggesting that the lubricant’s effect becomes negligible and the strain rate itself becomes the dominant factor. The material’s flow stress was characterized using the calibrated Johnson-Cook constitutive model. Based on the experimental data, a new explicit mathematical function describing the nonlinear dependence of friction on strain rate was proposed. This model was subsequently verified via finite element method simulations, showing high agreement between the predicted and experimental shapes of the deformed rings.