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 ofTi 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 l e,1 or e" the smaller displacement on nanoindentation.

Densification modeling of fused silica under nanoindentation

“…Such assumptions range from 2D equivalence of the 3D shape of the tip and angle of the pyramidal shape of the tip to most importantly the tip bluntness [12][13][14][15][16][17][18][19]. Although these assumptions may produce satisfactory results at deep indentations where the tip can be assumed ideal, inaccurate results appear at shallow indentations below 200 nm [3].…”

Numerically assisted nanoindentation analysis

“…Attempts to account for tip rounding included empirical equations [1] and non linear fitting algorithms [2]. Chen et al [16] have also shown that the errors in the angles of a pyramidal tip will result in significantly different force curves.…”

The compensational boundary method to calculate the projected contact area of nanoindentation in atomistic simulations

“…The AFM can be used to directly measure the area function, rather than the actual contact area due to the elastic recovery of tested materials during withdrawal of the indenter [7,8]. Additional corrections must be made for the evaluation of the PCA due to the imperfect indenter geometry, the tilt and surface defects of samples, and the pile-up/sink-in behaviour of tested materials [9][10][11][12][13].…”