Mechanics of hydrogen embrittlement

Finite element analysis has been used to model the mechanics of hydrogen embrittlement at a crack tip.;In the case of non-hydride forming systems, hydrogen diffuses to the vicinity of the crack tip and affects the elastic-plastic behavior of the materials. In addition, the state of stressing modifies the diffusion paths. Large deformation elastic-plastic analysis at a blunting crack tip coupled with hydrogen diffusion in the material has been carried out to study the mechanics of the phenomenon. The results show that hydrogen can accumulate at microstructural defects-traps at much larger concentrations than at normal interstitial lattice sites. In this context the mechanics of hydrogen related fractures is assessed.;In the case of hydride forming systems, combined mechanical effects and hydrogen diffusion cause hydride precipitation at the crack tip. The hydrogen transport along with the stress induced hydride formation has been modelled in an elastically deforming two-phase composite material. The size, shape and density of the hydride zone has been predicted. This result is used to explain the substantial reduction of fracture resistance in those materials.