Verification of Variable Amplitude Fatigue Life Methodologies for a Cast Aluminum Alloy

The objective of this research was to determine the feasibility of applying commonly used fatigue life calculation models to notched cast aluminum alloy components. Notched ‘component-like’ specimens made of A356-T6 cast aluminum alloy were used to obtain experimental fatigue lives both to the formation of a 1.5 mm ‘initiation’ crack and to final fracture. A commercially available fatigue life calculation software package was then used to calculate the fatigue crack initiation and propagation life corresponding to these tests, using a variety of common analysis methods. The resulting correlation between these experimental and calculated fatigue lives ranged from excellent to extremely poor (correlation ratios ranging from 1 to 10²), depending on the analysis method used. The wide range in correlation was due mainly to the large differences obtained from the fatigue crack growth life calculation methods. Extreme care must thus be taken when using these fatigue life calculations for cast aluminum alloys.