Closure-free intrinsic threshold stress intensity, ΔK_th,i, varies significantly as a unique function of near-tip residual stress. It does so in equal measure in 5 mm and 50 mm thick compact tension specimens. Specially designed load sequences employing marker loads are employed to fractographically characterize the effect of load history on fatigue crack growth rate under closure-free conditions in 7075-T6 Al-alloy. Observed variations correlate with ΔK_th,i, confirming that near-tip residual stress operates as an independent load interaction mechanism. A certain ‘micro latency’ before crack arrest due to increased ΔK_th,i is investigated under different gaseous environments through experiments involving hold time.

无闭合固有阈值应力强度 ΔK _th,i作为近尖端残余应力的独特函数而显着变化。它在 5 毫米和 50 毫米厚的紧凑拉伸试样上的测量结果相同。使用标记载荷的专门设计的载荷序列被用于断面表征载荷历史对 7075-T6 铝合金在无闭合条件下疲劳裂纹扩展速率的影响。观察到的变化与 ΔK _{th,i 相关}，证实近尖端残余应力作为独立的载荷相互作用机制起作用。通过涉及保持时间的实验，研究了在不同气体环境下由于 ΔK _th,i增加而导致裂纹停止之前的某个“微潜伏期” 。