Surface Separation and Contact Resistance Considering Sinusoidal Elastic-Plastic Multiscale Rough Surface Contact

Abstract

This thesis considers the multiscale nature of surface roughness in a new model that predicts the real area of contact and surface separation as functions of load. This work is based upon a previous rough surface multiscale contact model which used stacked elastic-plastic spheres to model the multiple scales of roughness. Instead, this work uses stacked 3-D sinusoids to represent the asperities in contact at each scale of the surface. By summing the distance between the two surfaces at all scales, a model of surface separation as a function of dimensionless load is obtained. Since the model makes predictions for the real area of contact, it is also able to make predictions for thermal and electrical contact resistance. For the specific case of thermal contact resistance, scale-dependent surface characteristics are taken into account in this model. In the field of contact mechanics, concern has been voiced that the iterative calculation of the real contact area in multiscale methods does not converge. This issue has been addressed with results not only confirming convergence but also giving the conditions necessary for the sinusoidal based multiscale method to converge. To further verify the results of this new method, all results and calculations are compared to previous works that were based upon statistical mathematics to model contact area and load. These comparisons have given qualitative support to the sinusoidal multiscale technique featured here as well as revealing some possible short-comings of the statistical techniques, particularly in the area of surface separation calculations. Upon further investigation, a correction is proposed in this work that alleviates this short-coming for statistical contact modeling. The multiscale sinusoidal based elastic-plastic modeling technique is calculated and compared for a variety of surfaces, each with a differing roughness with appropriate results. Finally, in an effort to experimentally validate the electrical contact resistance theoretical results, the initial setup and outline behind an experimental test rig is explained.