  We present a phase field modeling framework for hydrogen assisted cracking.
The model builds upon a coupled mechanical and hydrogen diffusion response,
driven by chemical potential gradients, and a hydrogen-dependent fracture
energy degradation law grounded on first principles calculations. The coupled
problem is solved in an implicit time integration scheme, where displacements,
phase field order parameter and hydrogen concentration are the primary
variables. We show that phase field formulations for fracture are particularly
suitable to capture material degradation due to hydrogen. Specifically, we
model (i) unstable crack growth in the presence of hydrogen, (ii) failure
stress sensitivity to hydrogen content in notched specimens, (iii) cracking
thresholds under constant load, (iv) internal hydrogen assisted fracture in
cracked specimens, and (v) complex crack paths arising from corrosion pits.
Computations reveal a good agreement with experiments, highlighting the
predictive capabilities of the present scheme. The work could have important
implications for the prediction and prevention of catastrophic failures in
corrosive environments. The finite element code developed can be downloaded
from www.empaneda.com/codes
