Criterion for surface contact deformation of metals

In most engineering applications, bulk plastic deformation of the surface is avoided. There is, however, no criterion for determining whether or not bulk plastic deformation occurs during the contact between rough surfaces. This paper presents a criterion for predicting the deformation behaviour of the contact between a real rough surface against a curved body. In order to verify the proposed criterion, experimental investigations were carried out for three different materials. It was found that the experimental results confirmed the proposed criterion very well. For a given operational contact condition, a contact system where bulk deformation does not occur can be designed using this criterion. If the criterion value C_m is less than 0.52 plastic deformation occurs on asperity level only and there is no bulk deformation, but if C_m is greater than 0.52 there are two possible deformation modes, i.e. plastic deformation of the bulk and plastic deformation in both the asperity and the bulk. Copyright © 2006 John Wiley & Sons, Ltd.