AMPLITUDE DISTRIBUTION ANALYSIS OF ACOUSTIC EMISSION DURING FATIGUE TESTING OF STEELS USED IN OFFSHORE STRUCTURES.

An analysis of amplitude distribution of acoustic emission (AE) signals during fatigue testing of low-strength, low carbon steel specimens used extensively in the fabrication of off-shore structures was carried out. The test results show three different amplitude distribution patterns which coincide with the three stages of fatigue reported in the literature. A statistical analysis showed that the statistical parameters like mean, skewness and kurtosis are useful in distinguishing the three amplitude distribution patterns. An autocorrelation analysis of the time series showed that the second autocorrelation coefficient C2 varied most significantly between the three stages, (stage I: 0. 151; stage II :0. 0054; stage III: 0. 37). The first minimum in the autocorrelation function referred to as lagj(min) varied significantly.