Scale bridging modeling of hydrogen enhanced crack propagation in steels
Hydrogen Enhanced DEcohesion (HEDE) advocates that hydrogen atoms reduce the cohesive strength of interatomic bonds at crack tips or in areas with localized tensile strength and thereby promotes decohesion. The hydride formation and embrittlement mechanism suggests that cracking could proceed by the formation and cracking of a hydride at the sites of stress centers (e.g. crack tips) and at grain boundaries. The significance of these mechanisms depends on the materials and their service condition.
This project focuses on studying the HELP and HEDE (non-hydride formation) mechanisms. It takes the findings of other ICAMS projects and combines them into a single continuum model. Density Function Theory (DFT) studies reveal that the elastic constants and the cohesive energy decrease with increasing hydrogen concentration (see AMS-03-01 and AMS-01-04). Atomistic modeling on the HELP mechanism (see CMD-09-01) provides a possibility to derive hydrogen influenced kinetics of dislocation glide. Another crucial problem on continuum level is to quantify the diffusion of hydrogen atoms under external mechanical loading. This leads to a coupled deformation-diffusion problem.