Experimental investigation on double impulses phenomenon of outer race spalled rolling element bearings based on acoustic emission signals

Spalling on races and/or rolling elements are major fatigue failures of rolling element bearing (REB). Previous studies indicated that there will be double impulses phenomenon happened in the vibration when a rolling element rolling through the spalling zone. If the double impulses can be extracted, the size of the spalling might be calculated, and then the remaining useful life (RUL) of the bearing would be evaluated. So far, amount studies of the double impulses extraction, fault size calculation and the prediction of the RUL of the REB were discussed based on vibration, which has been used in rotational machine diagnosis. Recently, the acoustic emission (AE) signal based rotational machine diagnosis methods are attracted the researchers´ attention. The AE based techniques are more competitive than the vibration based techniques due to the advantages of the AE over the vibration. In this paper, the double impulses phenomenon in AE of outer race spalled REB were investigated. In the investigation scheme, Discrete Wavelet Transform (DWT) were used to enhance the characteristic AE generated by the spalling. Then the Hilbert based envelope analysis and low pass filtering was utilized to extract the double impulses. Experiment analysis indicates that, the double impulses phenomenon can be also found in AE of outer race spalled REB.