Weakly anisotropic residual contact stress in silicon demonstrated by electron backscatter diffraction and expanding cavity models

Abstract

The residual stress field surrounding an elastic-plastic spherical indentation contact in Si is determined by electron backscatter diffraction (EBSD)-based experimental measurements and expanding hemispherical cavity-based models. The experiments provide support for indentations as test vehicles for assessment of EBSD as a two-dimensional deformation mapping method but make clear that selection of coordinate axes is critical to determining the correct representation of a stress field. The use of principal stress coordinates rather than the conventional Cartesian coordinates is required in cases in which the direction of the stress field is not aligned with Cartesian axes. In particular, the use of principal coordinates in the analysis of a spherical indentation stress field in Si removed misleading artefacts from the Cartesian-based field and revealed only a weak effect of Si crystalline elastic anisotropy. The experimental results are supported by isotropic and anisotropic finite element analysis models.