Investigations of the fatigue damage in 16Mn steels by wavelet-based acoustic emission technique

16Mn steel is widely used in the large structural machines such as cranes. Fatigue is one of the most common failure modes in this material. Thus, monitoring of the fatigue damage in 16Mn steel is important for the health monitoring of these large engineering structures. In this paper, fatigue crack propagation tests were carried out for hot rolled and low temperature tempered 16Mn steels. Acoustic emission (AE) signals obtained from the fatigue tests were processed by wavelet packet transform (WPT) analysis. The energy distribution in each component of the AE signals was calculated for different specimens. Ratio of energy was extracted as a feature parameter. The results showed that the ratio of energy in each node was different in the hot rolled and low temperature tempered 16Mn steels respectively. The ratio of energy depended on the micro-structure. Based on the SEM fractography observations in this study, these results could be well explained by the different fatigue crack propagation mechanisms.