A Condition for Complete Flattening of Asperities in a Rough Contact

Considering rough surface profiles in a contact model is of decisive importance. In the up-to-date rough contact models there remained underexplored the opportunity of complete flattening of smaller asperities and therefore the need of using the multilevel roughness models, including fractal ones. If higher level asperities are not flattened completely when pressed, then they will be able to impact on the contact process. This paper considers model problems of elastic-plastic contact with hardening for a body with protrusions and two pyramids as the objects similar to asperities. Modeling results show that asperities are completely flattened only on condition of confined compression. For real contacting rough surfaces under low pressures, complete flattening of asperities will not occur. It is shown that roughness elements on the surface of the asperities do not disappear even at severe deformation of the latter. The reason is a combination of the asperity form and hardening of material, while the consequence is a reduction of the real contact area.