Prediction of Nano-Scale Wear- An Analytical Approach

摘要

When two surfaces touch each other, intimate contacts occur at the tips of the asperities and adhesional interaction between the solids arising out of the surface forces becomes significant. This effect need be considered in MEMs, micro-machines, magnetic storage systems and other such situations where the surfaces are inherently smooth and loads are extremely low. Surfaces in these and many other tribological contacts may have sub-micron or even nanometric levels and the stochastic model for rough surfaces that typically applies to engineering surfaces is not suitable. The rough surface model in these circumstances must cover asperities ranging from nanometer to micrometer level and this essentially needs a fractal approach. The paper describes a theoretical study of adhesive wear at the contact between surfaces with nanometric level asperities at low loads using a fractal contact model and taking into account the surface forces. The model predicts wear between solids with wide range of material and surface properties. The results broadly confirm the experimental observation such as dependence of wear volume on normal load and also on adhesion due surface forces. Furthermore the fractal analysis gives a generalized solution and depending on the combinations of material and fractal parameters specific solutions, relevant to realistic situations may be arrived at. are obtained. Under certain parametric combinations high wear even under tensile load is predicted while near zero wear is expected for some another set of parameters. These predictions are certainly advantageous in the selection of surface and material properties in applications where loads are small and surfaces are ultra smooth.