38 Effects of Cyclic Plastic Strain on Hydrogen Environment Assisted Cracking in High-Strength Steel

Cyclic loading tests were performed on micro-notched samples of high-strength steel S690QL (standard EN 10137-2) in air and under cathodic polarization in a saline solution. These specimens were modeled and their behavior simulated by finite elements calculations with a combined nonlinear isotropic-kinematic hardening constitutive law. This model can simulate cyclic softening and ratcheting effect of the high-strength steel. Stress and strain fields in the vicinity of the notch-tip were calculated. Results show a strong dependence of the crack initiation with plastic strain accumulation. Hydrogen assisted cracking mechanism is discussed based on arrangements of dislocations structures.