Residual stresses in high pressure die castings

This study has compared different methods for measuring residual stresses in high pressure aluminium castings. The hole-drilling and X-ray diffraction method were used. A stress lattice were used. The results from the measurements were then compared with simulations of residual stresses. The effect of different heat transfer related parameters were investigated and correlated to measurements. It has in present work been shown that deviations in measured stresses is to be expected, especially at the surface and in positions where large stress gradients are present. Compressive stresses were the dominating stresses at the surface for all measuring points. The principle stresses then increased inwards. The simulations were based on both qualitative and quantitative aspects. Both relaxation of strains during drilling and stresses were evaluated and compared to measurements. The initial heat transfer coefficient (h0) in combination with a highly resolved model the first millimeter had the largest impact on the simulation results. The use of an extremely high h0 gave the best results, both from a qualitative and quantitative aspect. A high h0 gave lower stresses at the surface compared with a lower h0. The stress gradient inwards from the surface were also in better conformity compared to a low h0. The stresses at 1 millimeter were not however influenced at all from the h0. Simulations were also performed on two industrial components, one die and one high pressure cast. However, they had been subjected to different post-processing steps after they were cast, one shoot peened and one T6-treated. Therefore no valid comparisons could be performed