Damage tolerant structures require accurate fatigue crack growth rate models for life prediction. Central to these models are fracture mechanics similitude and empirically gathered growth rates. In this work, standard test methods failed to achieve similitude for 17-4PH stainless steel round-rod but succeeded for plate. Material product form differences are interrogated through constant ΔK tests, crack path analysis, residual stress (RS) characterization, and growth rate simulation. Analyses revealed that quench-induced RS in the round-rod promoted a non-planar, 3D crack path with closure effects. Strategies to mitigate the RS/path effects are evaluated by controlling constraint, closure, environment, and heat treatment.

耐损伤结构需要准确的疲劳裂纹扩展速率模型来预测寿命。这些模型的核心是断裂力学相似性和经验收集的增长率。在这项工作中，标准测试方法未能实现 17-4PH 不锈钢圆棒的相似性，但板材成功了。通过恒定 ΔK 测试、裂纹路径分析、残余应力 (RS) 表征和增长率模拟来审视材料产品形式差异。分析表明，圆棒中的淬火诱导 RS 促进了具有闭合效应的非平面 3D 裂纹路径。通过控制约束、闭合、环境和热处理来评估减轻 RS/路径效应的策略。