抄録
Three-point and four-point bending tests were carried out in water on the high strength Ni-Cr-Mo steel quenched and tempered at 653 K in order to investigate the effect mixed mode I-II loading on tte crack propagation and crack branching in delayed failure. The crack propagation velocity before crack branching was almost independent of the ratio of mode II to mode I stress intensity factor when it was within 0.3. Both the crack branching angle and the deviation of crack branching angle to the crack propagation direction before crack branching increased with increase in the ratio of mode II to mode I stress intensity factor. The above results were explained by an criterion which was introduced by combining the hydrostatic tensile stress and the hydrogen concentration at a crack tip.
