Among many amplitude parameters, Kurtosis and Bicoherence are recognized to be the sensitive good parameters for machine diagnosis. In this paper, simplified calculation method of coefficient of autocorrelation function of 1st order lag is introduced, and new deterioration factor of correlation of four variables is introduced consecutively. New deterioration factor is an absolute index of deterioration factor. The case in which the rolling elements number is nine is examined. Varying N, the number of data, its characteristics are examined. When N is smaller, sensitivity is better. Therefore this parameter can be used as an index for the machine diagnosis of early failure stage especially.
Mathematics Subject Classification: 60G35
Keywords: impact vibration; deterioration; autocorrelation function; rolling element