Abstract: The criterion of contact loss between pairing elements is an important problem in the field of dynamics of mechanism with clearances. It is the theoretical basis for the design of avoiding impacts, reducing noises and prolonging the life of mechanisms. According to theoretical analyses, this paper points out the deficiencies of the oriterien which is now used and puts forward a new, more effective criterion. The correctness of this new criterion is verified by calculating the dynamic response of a planar four-bar mechanism with clearances.

Key words: 分离, 间隙, 平面连杆机构, 运动副