SUBSURFACE DAMAGE INVESTIGATION BY HIGH-FREQUENCY ULTRASONIC ECHOGRAPHY ON 100CR6 BEARING STEEL

This paper presents an original ultrasonic technique devoted to the ea rly detection of sub-surface fatigue cracks in 100Cr6 bearing steels. Echographic experiments were carried out during interrupted rolling co ntact fatigue tests, Crack initiation and crack propagation stages wer e both investigated, Quantitative measurements of sub-surface crack po sition, depth and angle with respect to the bearing surface are presen ted. Experimental results are analysed and discussed in relation to ro lling contact fatigue theories, Contrary to what is generally accepted the presented results show that the crack propagation stage could rep resent an important part of bearing life. (C) 1997 Elsevier Science Lt d.