Simulation and Measurement of Residual Stresses for HCF Cracks on LPDC Aluminium Cylinder Head

The differences in mould filling, solidification and molten alloy cooling in variable sections arising from both casting practice and design lead to extremely varying residual stresses. Residual stresses, unless eliminated or reduced, can exceed the fatigue endurance limit together with the operational stresses and finally lead to premature cracking. The effect of quenchant on the residual stress was studied and subsequently cylinder head quenching operation was performed by using water, water - polymer mixture and air. Residual stress measurements have shown the highest stresses to occur at locations where cracks were observed. Simulation results were verified by experimental measurements of the residual stress distribution.