Defect Based Fatigue Life Predictions for Aluminum Castings

Aluminum casting parts generally have inherent internal defects such as porosity which lowers the fatigue strength of such castings. Accounting for such a fatigue strength reduction for Aluminum casted parts is the primary purpose of this paper. Authors have used Murakami et al [1] approach to calculate porosity correction factor for fatigue. The actual material S-N curve is modified using fatigue factors to account for the fatigue strength reduction due to presence of porosity. This approach was then validated on one of the fatigue failure cases on Aluminum casted housing. There was a close match between the test data and proposed approach for fatigue prediction. With this approach, engineers will be able to do fatigue predictions in presence of material defects like porosity with simple porosity correction factor, rather than using complex modeling of porosity in FEA or using detailed fracture mechanics methods. Engineers can also be able to provide acceptable levels of porosity in castings based on the methods suggested in this paper.