I am currently undertaking a module in Failure Analysis, one topic of which is vibration monitoring of bearings. During this study, the notion of first and second Kerr diagrams as a tool for analysis came up. I have been trying to find additional information on Kerr diagrams; however, outwith the lecture notes, there appears to be none. I have consulted the recommended reading list, Google, and spoken with professional engineers working in condition monitoring -- none of which has been able to provide any insight. In fact, outwith the lecture notes, there seems to be no trace of their existence. My question is whether anyone on this form is familiar with Kerr diagrams and if possible, could point the way to additional reference material? Thanks.