Molecular Dynamics Numerical and Experimental Analysis of Fretting Wear Mechanism of Variable Gauge Bogie

Abstract

Under the "One belt, One road" strategy, the trade in goods is more frequent in diverse countries. The difference in train gauge between countries often leads to low efficiency of freight transportation. In several schemes, the variable gauge bogie can efficiently solve this problem. The fretting wear between the axles and wheels of train gauge changeable bogies may cause the connection relaxation and failure in the actual working process, resulting in potential safety hazards. Diverse experimental researches show that surface treatment technology can effectively reduce the friction and wear between axles and wheels. However, its micro wear reduction mechanism is not clear, to date. Therefore, the three-dimensional fretting wear model of bogie axle and wheel is established by molecular dynamics method in this paper. The wear reduction mechanism of surface treatment technology is then clarified from the micro point of view, and also verified by experiments. The results show that there is micro convex contact between the two surfaces under the contact stress. The micro convex is extruded and deformed, hence forming an adhesion. Whereas, the convex adhesion is desorbed by the shear force during separation, resulting in fretting wear. Since the wear reduction is caused by the reduction of transverse force, good lubrication and wear reduction effect can be achieved by MoS2 coating and nitriding. The surface treatment of MoS2 coating also reduces the friction coefficient between axles and wheels along with improving load bearing. Whereas, the friction coefficient can be decreased by increasing the nitriding amount.