A numerical approach to indentation technique to evaluate material properties of film-on-substrate systems

Spherical indentation approach (Lee et al., 2005, Lee et al., 2010) for the evaluation of bulk material properties is extended to that for elastic–plastic properties of film-on-substrate systems. Our interest focuses on single isotropic, metallic, and elastic–plastic film on a substrate, and we do not consider the size effects in plasticity behavior. We first determine the optimal data acquisition location, where the strain gradient is the least and the effect of friction is negligible. Dimensional analysis affords the mapping parameters as functions of normalized indentation variables. An efficient way is further introduced to reduce both the number of analyses and the regression order of mapping functions. The new numerical approach to the film indentation technique is then proposed by examining the finite element solutions at the optimal point. With the new approach, the values of elastic modulus, yield strength, and strain-hardening exponent of film materials are successfully obtained from the spherical indentation tests. We have shown that the effective property ranges such as indenter properties, substrate modulus, and E/E_s ratio can be extended without additional simulations and even loss of accuracy. For other ranges of variables or other properties, which are not dealt with in this study, this methodology is applicable through resetting FEA variables and finding proper normalized parameters.