Crack Initiation and Propagation in RCF – A New Approach to Understanding Pitting Failure of Highly Loaded Gears 2006-01-0383

Model testing for rolling contact fatigue (RCF) strength is an important tool for pre-selecting materials and processes for highly loaded gear applications. S-N curves based upon final and catastrophic failure are used to compare material compositions and effects of process parameters in order to improve life time until fracture. The introduction of eddy current technology to detect cracks in the very early stages of nucleation is about to change failure definition in RCF and allows a completely new approach to understanding initiation and propagation of flaws and failures in RCF. This paper describes the fundamental principle of eddy current technology in RCF testing and presents first results on wrought and PM steels. It also contains first test results on crack propagation at different levels of contact pressure, even below the “endurance” limit. The practical consequences of the new approach will be discussed, as well as the impact on future model testing procedures.