Adhesion in the Contact of a Spherical Indenter With a Layered Medium

With the emergence of micro- and nano-technology, the contact mechanics of MEMS & NEMS devices and components is becoming more important. The motivation for this work is to gain a better understanding of the role of coatings and thin films on micro- and nano-scale contact phenomena, and to understand the interactions of measurement devices, such as an Atomic Force Microscope (AFM), with layered media. The frictionless contact between a rigid spherical indenter and an elastic layered medium is the subject of this research. This configuration can be viewed as either a single asperity contact or as a building block of a multi-asperity rough surface contact model. As the scale decreases to the nano level, adhesion becomes an important issue in this contact problem. The presence of adhesion affects the relationships among the applied force, the penetration of the indenter and the size of the contact area. This axisymmetric problem includes the effect of adhesion using the Maugis model. This model spans the range of the Tabor parameter between the JKR and DMT regions. Key parameters have been identified which are the elastic moduli ratio of the layer and the substrate, the Poisson’s ratios, the dimensionless contact radius, the dimensionless layer thickness, and the adhesion parameter λ.