Investigation of Crack Growth Characteristics for EH690 Marine Steel Using Acoustic Emission Wavelet Energy Entropy

The fatigue crack growth (FCG) of 690 MPa grade offshore steel has been investigated. The characteristic acoustic emission (AE) parameters of EH690 steel compact tensile (CT) specimens during FCG were measured, and the FCG response was quantified in terms of AE count (CNTS). The energy entropy of each wavelet ( E S ) was calculated to establish the relationship between the AE wavelet energy entropy rate (d E S /d N ) and the stress intensity factor range(Δ K ) during the crack stable growth stage. The results indicate: (1) A linear correlation between AE cumulative count and cycle number ( N ) across stress ratios ( R = 0.05, 0.1, 0.3, and 0.5), e.g., the N to grow from 21 to 32 mm crack length the base metal (BM) is less than the weld metaland the heat‐affected zone. (2) The AE CNTS exhibits greater dispersion with respect to the N , which is beneficial for the characterization of plastic deformation in the crack tip region. (3) Log–log plots of d E S /d N versus Δ K are linear correlated with the slope of the fitted line increasing from 2.81 ( R = 0.05) to 5.26 ( R = 0.5) for BM. (4) E S is highly concentrated with respect to the N , serving as an effective parameter for characterizing crack growth.