<i>K</i>‐DOMINANCE CONDITION IN HYDROGEN ASSISTED CRACKING: THE ROLE OF THE FAR FIELD

Abstract

Abstract— This paper analyses the validity of the fracture mechanics approach to hydrogen assisted cracking in metals on the basis of K ‐dominance over both the stress‐strain state and the accumulation of hydrogen in the fracture process zone. Stress‐strain assisted diffusion of hydrogen is considered as the rate controlling factor of hydrogen assisted cracking under sustained or quasi‐static loading conditions. The discrepancy in the crack tip zone between the far‐field affected diffusion and the asymptotically driven ( K ‐controlled) process is elucidated. The far field (i.e., the stress‐strain field which is not K ‐dominated) is shown to have a minor effect on near‐tip hydrogen diffusion. It can only widen the scatter band of crack growth rates in the near‐threshold portion of the crack growth kinetics curve.