Influence of natural defects on the fatigue limit of a cast Al-Si alloy

Experimental high cycle fatigue tests have been performed in order to define the impact of casting shrinkages on the fatigue limit of the A357-T6 cast Aluminum alloy. Both cavity and sponge shrinkages have been analyzed. The effect of the defect morphology on the fatigue limit has been investigated for natural and artificial surface defects. The stress / strain distribution around a natural cavity shrinkage has been investigated by means of µ-CT analysis and finite elements simulations on the real defect shape. The results obtained on the real defect morphology have been compared with two equivalent geometries: a sphere and an ellipsoid.