Rough Surface Plasticity and Adhesion across Length Scales

Abstract

The study of interacting rough surfaces, especially at mesoscale and nanoscale, has been playing a central role in a broad spectrum of novel applications, e.g. nanostructure fabrication and reliability. The multiscale nature of surface roughness, the structure- and size-sensitive material deformation behavior, and the importance of surface forces and other physical interactions give rise to very complex surface phenomena at mesoscale and nanoscale. In this work, we present a contact mechanics model based on the power spectral density function of the surface roughness. This is more relevant to large-scale rough surface contact with the use of classic plasticity theory. If using phenomenological strain-gradient plasticity theory, we can show that one can only flatten asperities in a certain frequency interval of the roughness spectrum. We also present a new scheme of modeling rough surface adhesion by using the Dugdale model and the self-affine fractal surface, which leads to a discussion of gecko adhesion. We also present some of our perspectives about the interaction between adhesion and micro-plasticity for, e.g., nano-imprinting and nano-welding applications.