Monitoring damage by acoustic emission in bearing steels in cryogenic environment

Fatigue is the usual type of damage occurring at heavily loaded hertzian co ntact zones such as those found on bearings. An in-depth knowledge of the o rigins and evolution of fatigue-induced damage is crucial for correctly for eseeing the life span of mechanical parts. In order to monitor crack-initiation during an extremely low-temperature (c ryogenic) fatigue test, acoustic emission measurements were used. In this present study we show that the analysis of those signals emitted du ring testing is a reliable means of distinguishing and quantifying the firs t two stages of fatigue-induced damager namely microscopic crack-initiation and crack-growth. The after-the-fact analysis of failed test specimens: (t heir autopsy, so to speak) provides us with a detailed picture of these sta ges by revealing the crack-initiation zones and the way in which they grow. (C) 2001 Published by Elsevier Science Ltd.