Evaluation of hydrogen assisted cracking: the meaning and significance of the fracture mechanics approach Original Research Article

Analysis of hydrogen assisted cracking is performed with emphasis on the validity of the linear elastic fracture mechanics approach. Its soundness is ensured by the uniqueness of the crack growth kinetics curve `crack growth rate v versus stress intensity factor Kʹ for a material–environment system. The ability of this relationship to match the similitude of crack tip events is revised for the whole chain of process components: `hydrogen supply to metal—entry into and accumulation in the process zone—degradation and crack advanceʹ. Some of the factors able to violate the uniqueness of the `materialʹsʹ v(K)-curve are discussed: (i) the role of far field in hydrogen transportation to the fracture zone; (ii) near tip environmental interactions and process zone hydrogenation dependent on the cracking process history; (iii) mechanical nonlinear effects caused by crack tip plasticity which may be significant even under small-scale yielding. Suggestions for a refinement of the customary fracture mechanics approach are given.