Fatigue behaviour of notched ADI castings

Abstract

This work aims at studying the capability of mechanical stress analysis software (ANSYS 12.0) as a non-destructive tool to characterise and quantify the fatigue strength of notched austempered ductile iron (ADI) castings with different radii (from 1 to 3 mm). Castings were made of ductile iron with a chemical composition of 3.55C-2.18Si-0.35Mn-0.022P-0.008S-0.045Mg. The samples were heat treated by austenitising at 900 degrees C for 1 h and then rapidly quenched into two different salt baths at 350 and 400 degrees C for 1 h each. Because the properties of the samples austempered at 350 degrees C were matched with the ASTM standard for ADI alloy grade 2 (1050-700-07), the fatigue strength of the samples austempered at 350 degrees C was first predicted using a mechanical stress analysis software (ANSYS 12.0). To verify these theoretical results obtained by ANSYS 12.0, experimental fatigue tests using rotating bending fatigue machine at high stress regime were performed on the samples austempered at 350 degrees C. The fatigue samples were machined with different radii of 1, 1.5 and 2 mm. The results showed that the predicted fatigue strength by ANSYS 12.0 is very close to the experimental one. In addition, both austempering temperatures of 350 and 400 degrees C showed relatively similar notch sensitivity factor q, and its value decreased with increasing notch radius