Some observations from acoustic emissions recorded during a yield test of a bearing raceway compressed into plasticity using a rolling element are presented. The general objective of the study is to establish whether there is enough evidence of the onset of sub-surface plasticity in the acoustic emissions signature. It is discussed here how acoustic emissions monitoring during compression could indicate the onset of subsurface plasticity as a precursor to damage propagation to the surface. Some comparisons are drawn between the acoustic emissions activity levels and time-frequency response during elastic deformation and at yield loads.
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