A comparison of the predictions of a multiscale model and optical real area of contact measurements

Rough surface contact is difficult to model effectively due to the existence of multiples scales of geometrical features (i.e. asperities). There are many different methodologies in the literature to theoretically predict the real area of contact, but few of these have been compared directly to experimental data. This is because it is very difficult to measure the real area of contact between surfaces due to an obstructed line-of-sight and the very small scale of the surface features that are in contact. This work presents the predictions of a multiscale rough surface contact model in comparison to measurements made of the real area of contact between a transparent glass surface pressed against a metallic surface. A laser profilometer is used to scan the deformed profile of the surface and therefore the contact area can be measured. The multiscale model is able to account for the resolution of the measurement by neglecting smaller scales of features. The multiscale model compares well with the measurements at low loads, but not at high loads. The real contact pressure predicted by the multiscale model and measured are both much higher than conventional hardness that is often used to predict the real area of contact.