Characterization of Void Coalescence in Alpha-Iron in the Presence of Hydrogen

Abstract

Characteristics of void coalescence process due to hydrogen load effects in the multiple void array are simulated using the finite element method. The goals of this paper are to characterize the effects of hydrogen on the void coalescence process within the multiple void array, and to determine the void array and void volume fraction configuration in which hydrogen has the strongest effect on the occurrence of void coalescence. We use the couple analyses between the large deformation elastic-plastic analysis in the presence of hydrogen for structural analysis and hydrogen diffusion analysis using the hydrogen enhanced localized plasticity (HELP) theory. These coupled analyses are applied to the five different models with the different void volume fraction and void array. The numerical results show that both hydrogen and the void characteristics - void array and void volume fraction - affect metallic material failure. The internal necking void coalescence occurs in the square void array while the void sheet mode of coalescence occurs in the diagonal void array. Hydrogen has the strongest effect on the occurrence of void coalescence when the void volume fraction is large and the void array is square, induces a pronounced localized plastic deformation at the ligament between voids, and is present in high concentrations in regions with high values of the equivalent plastic strain.