ABSTRACT
During unloading, adhesion forces play an important role. Adhesion contact established during loading is capable of appreciable plastic extension before fracture, especially for materials with high modulus and low hardness. If we take into account the condition that plastic deformation of the material during loading is followed by ductile extension of the contact, then a criterion for ductile extension is given by [14]
Here it is assumed that the tip of microasperity will extend in a ductile manner when the contact pressure just exceeds the hardness H of the material during unloading. Generally, the softer the material, the greater the possibility of plastic extension before fracture [14].
