Acoustic emission at the wheel-rail contact with micro-slip and stick-slip

The paper aims to analyse the occurrence of acoustic emission at the wheel-rail contact during micro-slip. The experimental model allows the contact pressure variation (MPa..GPa) and the sliding speed (0.01 to 0.5 mm/s) specific to the wheel-rail contact. It is determined experimentally and theoretically the appearance of the stick-slip phenomenon at the Hertzian contact of cylinder type (fixed-wheel specimen) - plane (mobile with very low speed - rail specimen). The experimental stand simultaneously measures the normal force, the friction force and the acoustic emission at different contact pressures, sliding speeds and rigidities of the wheel specimen fixing system. The specimens are made of UIC standard materials used in the driving wheels and rails. The stick-slip phenomenon occurs at low micro-slip speeds and normal bending stiffness. Experimentally, it is found that the jumps specific to the stick-slip phenomenon( friction coefficient-COF) are accompanied by the acoustic emission (AE) at the cylinder-plane interface. The energy emitted by AE (WAE) is correlated with the energy consumed by friction during the stick-slip period (WCOF). The theoretical model regarding the stick-slip phenomenon of the Hertzian contact with slip specific to the experimental stand allows the analysis of the stability of the stick-slip movement.