Study of the effect of imperfect tips on nanoindentation by FEM

Abstract

In this paper, the imperfect tip effect of the Ti film on Si substrate on nanoindentation with Berkovich probe tip was investigated with the finite element method (FEM). In the literature, we found the effects of tip deformation and tip radius on nanoindentation were investigated frequently, but the imperfect centerline of tip has never been studied. In this work, at first, the Ti film on Si substrate was conducted with a high-resolution nanomechanical test. The Young’s modulus of Ti films can be obtained by using the Oliver and Pharr method while the nanoindentation depth is smaller than 20% of the film thickness for avoiding the substrate effect. Second, the FEM was employed to determine the yield stress of thin films because it cannot be found from nanoindentation. Finally, the load-depth of nanoindentation was compared between the experimental data and numerical results. The results show while choosing the suitable yield stress of films, the load-depth curves of numerical simulation were very close to the experimental curves with the imperfect effect being ignored. Moreover, it is concluded while the imperfect angles of tip were considered that the larger imperfect angles |θ x | orθ x , the smaller displacement on nanoindentation.