Experiments for Validation of Elastic-Plastic Fracture Modeling of Hydrogen Affected Materials

The mechanical behavior of a material of interest, 21-6-9 stainless steel, has been fully characterized in two states: as- processed and hydrogen charged. This characterization data is used to fit material model parameters to develop a good description of the material mechanical behavior in each state. Next, elastic-plastic J-integral validation experiments of increasing complexity were developed and conducted on the 21-6-9 stainless steel material in both states. In the simplest case, the fracture behavior of the material was tested using a planar CT specimen geometry. Although the planar specimen provided useful data for the first step in the validation process, three dimensional fracture specimen geometries were necessary to validate our analysis process in three dimensions. Subsequent experiments used three dimensional axisymmetric geometries and three dimensional asymmetric geometries, each of varying crack length ratios. These geometries proved to be very successful for experimentally quantifying the crack driving force, J in both material states. The experimental methods and results for these various fracture specimen designs are described herein. The results are also compared to finite element simulations of the experiments