Prediction of hydrogen induced delayed fracture initiation time of high strength steel using cohesive zone modeling

A sequential coupling calculation method on hydrogen induced delayed fracture was developed based on cohesive zone modeling (CZM) by using finite element program-ABAQUS. Using this method, the fracture initiation time was numerically predicted for circumferentially notched round bar specimen of AISI4135 high strength steel under a constant load after electrochemically pre-charged. The effect of various hydrogen contents was also considered. The results show that the hydrogen dependent CZM can be used in the prediction of failure in actual structures. The predictions of the time to fracture are in good quantitative agreement with the some experimental results. The delayed fracture occurrs when a critical hydrogen concentration at the location of max hydrostatic stress is reached by diffusion. The critical hydrogen concentration is not dependent on initial hydrogen content.