3D-FEM modeling of the microscopic stress field of forsterite aggregate under hydrostatic pressure: Significance of the crystal orientation

Three Dimensional Finite Element Method (3D-FEM) has been used to model the deviatoric stress field in a forsterite aggregate with a sandwich geometry: two forsterite cubes aligned in the same crystallographic orientation (the “breads”) sandwich a third forsterite cube (the “filling”), which might have an identical or different crystallographic orientation. The results show that there is no von Mises stress in the forsterite sandwich if the sandwiching and sandwiched forsterite cubes are aligned in the same crystallographic orientation. If the crystallographic orientations are different, however, von Mises stress and heterogeneous stress distribution occur both along the boundary and in the forsterite cubes. For the investigated P-T conditions (up to 6.4 GPa and 500°C), the resulted deviatoric stress is much lower than the yield strength of forsterite, so that higher P, higher T, or other means to create higher deviatoric stress is necessary, in order to constrain the yielding behavior of forsterite.