Polygonal wear seriously decreases the lifespan of a tire of a passenger car and adversely affects vehicle dynamic safety.The present paper builds a model that reflects the dynamic contact characteristics of the tire and reveals the mechanism and conditions of polygonal wear of a tire.The model describes the dynamic contact behavior of the tread block and considers the characteristics of dynamic friction between the road and tread of a rolling tire.Conducting numerical bifurcation analysis,the paper reveals the conditions for self-excited vibration of the tread,i.e.,the improper combination of the vertical load,wheel slip angle,tire pressure and vehicle speed considerably strengthen the lateral self-excited vibration of the tread,which is the direct vibrational source of abnormal circumferential polygonal wear.The polygonal wear of a tire occurs when a vehicle travels for a certain long distance at a so-called polygonal wear speed.The polygonal wear speed should induce lateral self-excited vibration on the contact tread of the tire and the frequency of the lateral self-excited vibration should be divisible by the rolling frequency of tire that is determined by the polygonal wear speed.Visible polygonal wear requires that the vehicle travels at a certain polygonal wear speed for a minimal distance to produce a stably developing polygonal wear pattern even for subsequent driving at variable speed.
