Time Domain Analysis Method of the Impulse Vibro-acoustic Signal for Fatigue Strength Characterisation of Metallic Material

This paper proposes an alternative statistical approach that can significantly characterise the fatigue strength property of metallic material. In this study, a simple impulsive excitation technique based on ASTM E1876 is conducted to measure the vibro-acoustic signal simultaneously using data acquisition consisted of an accelerometer-microphone configuration. The considered metallic material in the proposed design is composed of rectangular bar in cross section of medium carbon steel S50C, stainless steel AISI 304, cast iron FCD 500 and brass with a similar size of dimension as a specimen. To take into account the effect of noise existance, an alternative Z-stem filter de-noising technique is derived and applied to minimise the noise frequency components. Moreover, the effectiveness of this filtering technique is calculated. The filtered vibro-acoustic signal has been statistically analysed using an alternative time domain analysis method known as Mesokurtosis Zonal Nonparametric (M-Z-N). The accurate curve fitting equation for every metallic material is obtained using the combination of the calculated M-Z-N coefficient for vibration and acoustic impulse signals. The fatigue strength characterisation is carried out by the comparison of the experimental results with fatigue strength properties obtained in the literature. Correlation between the slopes of the curve fitting and fatigue strength values validate the proposed method.