Artificial indentations for the study of contact fatigue of austempered ductile iron (ADI) discs

Abstract

Following previous works in which artificial indentations were used to speed up surface damage in steel components [W. Cheng, H.S. Cheng, L.M. Keer, Experimental investigation on rolling/sliding contact fatigue crack initiation with artificial defects, Tribol. Trans. 37 (1994); H. Fan, L.M. Keer, W. Cheng, H.S. Cheng, Competition between fatigue crack propagation and wear, J. Tribol. 115 (1993); W. Cheng, H.S. Cheng, L.M. Keer, Longitudinal crack initiation under rolling contact fatigue, Tribol. Trans. 37 (1994); W. Cheng, H.S. Cheng, L.M. Keer, X. Ai, Surface crack initiation under contact fatigue: experimental observation and contact analysis, ASME Trans. 115 (1993)], twin-disc tests were performed using artificially indented austempered ductile iron (ADI) discs. These tests were closely monitored and included detailed video microscopy observation of contacting surfaces and indentations neighbourhood. Post-test analysis included optical and scanning electronic microscopy of surfaces, sub-surfaces and indentations. The evolution of surface damage near indentations was correlated with the number of cycles, applied contact pressure, material properties and also with surface failures that were observed on the contact track away from the indentations. A new method is proposed to study surface damage around the artificial indentations and parameters were developed to characterize and quantify surface damage in ADI discs.