A finite element based elastic-plastic model for the contact of rough surfaces

An elastic-plastic model for contacting rough surfaces that is based on accurate Finite Element Analysis (FEA) of an elastic-plastic single asperity contact is presented. The plasticity index W is shown to be the main dimensionless parameter that affects the contact of rough surfaces. Below Psi = 0.6 the contact problem is purely elastic and above Psi = 8 it is mostly plastic. The mean real contact pressure is found to be practically independent of the contact load, similarly to the material hardness in fully plastic contact. An elastic-plastic hardness in the form 0.4(1/Psi) H can therefore be used to relate the contact load and real area of contact. A comparison with the approximate CEB (Chang, Etsion, Bogy) model shows identical results for pure elastic contacts having plasticity index values below 0.6 but substantial differences for elastic-plastic contacts having plasticity index values above 1.