Finite element modeling of the stresses, fracture and delamination during the indentation of hard elastic films on elastic-plastic soft substrates

In this work, the mechanical behavior of hard films on soft substrates was studied based on the finite element analysis of an indentation with normal forces. As an attempt to reproduce situations found in practice, defects we re considered during the preparation of the finite element mesh, both in th e film and at the interface. A sequence of steps was considered during the loading sequence applied in the models. Initially, the deposition (intrinsi c) and thermal (extrinsic) stresses were introduced to account for all resi dual stresses present in thin films deposited by processes such as sputteri ng. Later, a normal load of 50 N was applied on the pre-stressed system. Th e effects of a crack that propagated along the film/substrate interface was studied directly, by calculating the normal and shcar stresses that develo p at the film surface and the film/substrate interface, and indirectly, by looking at the behavior of cracks located at the film surface and propagati ng perpendicular to the interface. The results indicated that the suppressi on of the constraint imposed by the interface resulted in a decrease in the stresses in the film. However, the crack at the interface apparently did n ot interact with the stresses responsible for the array of circular cracks usually observed at the contact edge of the indentation of coated systems w ith soft substrates. (C) 2001 Elsevier Science B.V. All rights reserved.