Multi-asperity Contact Model Research Articles

An elastic–plastic finite element analysis of interacting asperities in contact with a rigid flat

A three-dimensional elastic–perfectly-plastic finite element model of asperity interaction has been developed. This model consists of two connected neighbouring deformable hemispheres which are brought into contact with a flat rigid surface. For two asperities of the same height and the same radius, as the approach of the rigid surface is increased, the contact area changes from two isolated nearly circular contacts to a wasp-waist area, and finally to a single oval shaped contact region. For asperities of different heights the results can be qualitatively similar to those for equal heights, but can also exhibit a shielding effect in which the first contact grows to eventually encompass the second lower peak. Results are given using dimensionless quantities for the force versus interference, and the contact area versus interference. These relationships are plotted for different asperity height differences and asperity separations. Also provided are graphs of the contact area boundary for different values of the approach. Curve-fit equations are presented as an aid in using this work as a building block in a statistical multi-asperity contact model which directly includes the effect of asperity interactions.

Contact modeling — forces

This paper reviews contact modeling with an emphasis on the forces of contact and their relationship to the geometrical, material and mechanical properties of the contacting bodies. Single asperity contact models are treated first. These models include simple Hertz contacts for spheres, cylinders, and ellipsoids. Further generalizations include the effects of friction, plasticity, adhesion, and higher-order terms which describe the local surface topography. Contact with a rough surface is generally represented by a multi-asperity contact model. Included is the well-known Greenwood–Williamson contact model, as well as a myriad of other models, many of which represent various modifications of the basic theory. Also presented in this review is a description of wavy surface contact models, with and without the effects of friction. These models inherently account for the coupling between each of the contacting areas. A brief review of experimental investigations is also included. Finally some recent work, which addresses the dynamics and associated instabilities of sliding contact, is presented and the implications discussed.