Threshold stress intensity factor of ultra-high strength steel (HV670) containing surface crack by hydrogen assisted cracking and cumulative elastic wave

摘要

In this study, elastic wave that occurred from the hydrogen-assisted cracking (HAC) of SKD11 (HV670) specimen was detected, and the frequency characteristics by hydrogen aggregation and crack propagation were analyzed by time-frequency analysis method using LabVIEW. Low-frequency bands below 40 kHz and high-frequency bands above 60 kHz were detected. Low frequencies below 40 kHz are due to hydrogen aggregation and corrosion, while high frequencies above 60 kHz are caused by crack occurrence and propagation due to HAC. The crack propagation of the specimen was observed from the cumulative elastic wave and the fracture surface, and K-IHAC was determined to be 1.96 MPa root m. This result provides basic data for the monitoring of structures for hydrogen-assisted cracking, and can be used to predict the HAC behavior of ultra-high strength steel.