The effect of dK/da on crack growth behavior of nickel base alloys has been studied by conducting stress corrosion cracking tests under positive and negative dK/da loading conditions on Alloys 690, 600 and X-750 in high temperature water. Results indicate that positive dK/da accelerates the SCC growth rates, and the accelerating effect increases with dK/da and the initial CGR. The FRI model was found to underestimate the dK/da effect by ∼100X, especially for strain hardening materials, and this underscores the need for improved insight and models for crack tip strain rate. The effect of crack tip strain rate and dK/dt in particular can explain the dK/da accelerating effect.

d K / d a对镍基合金的裂纹扩展行为的影响已通过在正，负d K / d a负载条件下在690、600和X-750合金在高温水中进行应力腐蚀开裂试验研究。结果表明，正d K / d a加快了SCC的生长速度，加速作用随d K / d a和初始CGR的增加而增加。发现FRI模型低估了d K / d a效果提高了约100倍，特别是对于应变硬化材料，这突显了需要改进裂纹尖端应变率的洞察力和模型。裂纹尖端应变率和d K / d t的影响尤其可以解释d K / d a的加速作用。