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A study of the mechanics of microindentation using finite elements

Published online by Cambridge University Press:  31 January 2011

T.A. Laursen  and
J.C. Simo
T.A. Laursen
Affiliation:
Division of Applied Mechanics, Department of Mechanical Engineering, Stanford University, Stanford, California 94304
J.C. Simo
Affiliation:
Division of Applied Mechanics, Department of Mechanical Engineering, Stanford University, Stanford, California 94304
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Abstract

In this paper the finite element method is used to explore the mechanics of the microindentation process. In the simulations discussed, aluminum and silicon are investigated both in their bulk forms and in thin film-substrate combinations. Among the quantities readily computed using this approach and given in this paper are hardness (computed using actual contact area), contact stiffness, effective composite modulus, and surface profile under load. Importantly, this investigation builds on previous work by providing a more critical examination of the amount of pileup (or sink-in) around the indenter in the fully loaded configuration, as well as the variation of the actual contact area during indenter withdrawal. A key conclusion of this study is that finite element simulations do not support the widely used assumption of constancy of area during unloading (for either bulk materials or thin film systems). Furthermore, the amount of pileup or sink-in can be appreciable. The implication of these findings is that for many situations the commonly used straight-line extrapolation of a plastic depth may render an estimate for the contact area that is quite distinct from the actual area. This assertion is demonstrated herein through comparison of hardnesses calculated using actual contact area with values calculated using the straight-line extrapolation of plastic depth.

Type
Articles
Information
Journal of Materials Research , Volume 7 , Issue 3 , March 1992 , pp. 618 - 626
Copyright
Copyright © Materials Research Society 1992

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