Ž . Thin Solid Films 392 2001 6574 Finite element modeling of the stresses, fracture and delamination during the indentation of hard elastic films on elastic plasti c soft substrates R.M. Souza a, , G.G.W. Mustoe b , J.J. Moore c a Surface Phenomena Laboratory, Department of Mechanical Engineering, Polytechnic School, Uni ersity of Sao Paulo, A. Prof. Mello ˜ Moraes 2231, Sao Paulo, SP 05508-900, Brazil b Di ision of Engineering, Colorado School of Mines, Golden, CO 80401, USA c ( ) Adanced Coatings and Surface Engineering Laboratory ACSEL , Colorado School of Mines, Golden, CO 80401, USA Received 3 May 2000; received in revised form 22 March 2001; accepted 22 March 2001 Abstract 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 were considered during the preparation of the finite element mesh, both in the film and at the interface. A sequence of steps was considered during the Ž . Ž . loadi ng seque nce appl ied in the mod els. I nitially, the depositio n intri nsic and the rmal extrinsic stress es were introd uced to account for all residual stresses present in thin films deposited by processes such as sputtering. Later, a normal load of 50 N was applied on the pre-stressed system. The effects of a crack that propagated along the film substrate interface was studied directly, by calculating the normal and shear stresses that develop at the film surface and the film substrate interface, and indirectly, by looking at the behavior of cracks located at the film surface and propagating perpendicular to the interface. The results indicated that the suppression of the constraint imposed by the interface resulted in a decrease in the stresses in the film. However, the crack at the interfac e appa rentl y did not inter act with the stresses respo nsible for the array of circular cracks usually observed at the contact edge of the indentation of coated systems with soft substrates. 2001 Elsevier Science B.V. All rights reserved. Keywords: Adhesion; Stress; Triboblogy 1. Introduction The dep osi tio n of coa tin gs is a wid esp read tec h- nology for improving the behavior of parts subjected to wear. These methods are particularly important in the case of sof t substrate s, such as alu min um, whic h are known for thei r poor trib olog ical prope rties 1 . In recent years, several processes were developed to deposit thin films on a substrate, each one associated with a series of process parameters that can signifi- cant ly affect the characte ristic s of the film 2 . There- Corresponding author. This paper was presented at ICMCTF 2000, San Diego, Califor- nia. fore, the number of possibilities to be tested for a given application is not restricted to the choice of the coating and its dimensions, but involves the selection of other factors, such as the process and its parameters. Since this number of possibilities is elevated, methods were dev elo ped to giv e ins igh ts int o the wea r be hav ior ofcoat ed syste ms without the need for long -term tests. Some of these methods refer to the use of analytical 3, 4 or finit e element anal ys es 58 to eval uate the contact str ess es ori ginated whe n the system is sub- jected to the normal andor tangential loads character- istic of many situations involving wear. In prev ious wor ks 911 , the authors pre sen ted a sequence of finite element analyses studying the con- tact stresses developed during the normal indentation of systems with an elastic plastic aluminum substrate 0040-609001$ - see front matter 2001 Elsevier Science B.V. All rights reserved. Ž . P II : S 0 0 4 0 - 6 0 9 0 0 1 0 0 9 5 9 - 2
