Modelling of non-steady-state transition from single-point to two-point rolling contact

By considering real wheel and track geometry and structures, as well as their coupled interaction, an explicit finite element method is applied to simulate the transition of wheel-rail rolling from single-point tread contact to two-point tread-flange contact. The evolutions of the contact position, stress magnitude and direction, adhesion-slip distribution, and wheel-rail relative velocities in the two contact patches are considered to investigate the transient dynamic effects during the contact transition. Important findings include that the transition to two-point contact can result in friction saturation and excite waves in the contact, causing local intensification and relaxation of compression, as well as turbulence of the micro-slip; the local relative velocity in the contact patch is a good measure of the dynamic effects.