Parametric computational analysis of indentation-induced shear band formation in metal-ceramic multilayer coatings

Shear band formation in multilayer thin-films subject to nanoindentation is studied numerically. The material system analyzed here is composed of alternating aluminum (Al) and silicon carbide (SiC) nanolayers, above a silicon (Si) substrate. Finite element models are developed to investigate system parameters that influence behavior of the shear band phenomenon. By introducing strain softening into the material model for the relatively hard ceramic layers, shear bands can be seen to emerge from the indentation site in the computational analyses. Effects of post-yield material parameter variations on the initiation of plastic instability are examined. Several geometric variations are also investigated, including the effect of relative layer thicknesses, homogeneity, layer order, and number of layers. The chain events that lead to shear band nucleation are postulated. Broad implications are noted, along with possible directions for future work.