3.2 Stress Finite Element Analysis: A non-linear stress FEA model using ANSYS software was used for simulating 3D residual stresses in a dented plate. Within the model, a round-bottomed punch was used to make a dent of 12mm diameter and depth 3mm in a mild steel plate of dimensions 40x40x3mm3. Below the plate was a die containing a hole of 18mm. The stress FEA results indicated two main regions of residual stress:
1. residual stresses in the dent rim, directed radially outwards from the dent centre. These were tensile at the top and compressive at the bottom of the plate.
2. residual stresses in the dent base, that were tensile at the top and compressive at the bottom.