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 π is shown to be the main dimensionless parameter that affects the contact of rough surfaces. Below π = 0.6 the contact problem is purely elastic and above π = 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 0.41/π H can therefore he 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.