On the mechanics of the hydrogen interaction with single crystal plasticity

This thesis presents a model to simulate the effects of hydrogen on the mechanical behavior of single crystals. A macroscopic crystal plasticity model is formulated based on the fundamentals of the hydrogen-dislocation interactions. Various hardening evolution equations are investigated and employed in a physically-based model. The presence of hydrogen is incorporated into the constitutive relations through basic equations to simulate its effects on dislocation activation, multiplication, and annihilation. The crystal plasticity model is then implemented in a computationally realizable solution to the single crystal uniaxial tension problem. The present model is designed within a crystal plasticity framework for an FCC single crystal. Features that incorporate the hydrogen effect into the constitutive model have been designed to directly capture observed effects in single crystals. Experimental data available in uniaxial tension for single crystal nickel specimens are used to calibrate the model. The sensitivities of the model are investigated through varying the magnitudes of the parameters controlling the mechanical behavior and how it is influenced by the presence of hydrogen. Through this study, a constitutive theory on how hydrogen affects the deformation is proposed and areas of further research are discussed