Elasto-Plastic Finite-Element Analysis of Stress Distribution in a Film-Substrate System Indented by a Spherical Indenter in Relation to Evaluation of Fracture Strength of Films.

Abstract

In electronic devices, magnetic disks and micromechanical systems, thin films are widely used. Improvement of their mechanical reliability requires invetigations of methods for evaluating fracure strength of thin films coated on substrates. In order to develop a method for evaluation of fracture strength by means of indentation with a small spherical indenter, an elasto-plastic finite-element stress analysis for the case of an elastic film and a plastic substrate is carried out in this paper. The analysis shows that radial tensile stress or occurs in the film beyond the contact area. An approximate equation for the distribution of σr is derived, which is useful for evaluation of the fracture strength.