Fatigue crack growth (FCG) behavior of SS 316(N) weld has been evaluated at different R‐ratios at room temperature and compared with that of the base metal. The FCG resistance of weld is better than that of the base material and is due to the residual stresses developed during the welding. The data were analyzed using the unified approach that considers the two‐parametric (ΔK and K_max) nature of fatigue. The R‐ratio effects in both the base and weld metals are accounted for without invoking the extrinsic parameters, such as plasticity‐induced crack closure. Since the residual stresses are of the monotonic type, they affect the crack growth via the K_max‐parameter. The crack growth trajectory plots were developed, and they show how the two crack tip driving forces, ΔK and K_max, change to overcome the FCG resistance of the weld in relation to that of the base metal. The results also show that the effects from the compressive residual stresses are more dominant at low R‐values and occur via the K_max parameter.

中文翻译：

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使用统一方法分析SS 316（N）焊缝的疲劳裂纹扩展行为

SS 316（N）焊缝的疲劳裂纹扩展（FCG）行为已在室温下在不同的R比下进行了评估，并与母材进行了比较。焊接的FCG电阻优于基础材料的FCG电阻，这是由于在焊接过程中产生的残余应力所致。使用考虑了疲劳的两参数（ΔK和K _max）性质的统一方法对数据进行了分析。在不调用外部参数（例如塑性诱导的裂纹闭合）的情况下，考虑了母材和焊缝金属的R比率效应。由于残余应力属于单调类型，因此它们会通过K _max影响裂纹扩展-范围。建立了裂纹扩展轨迹图，它们显示了两个裂纹尖端驱动力ΔK和K _max如何变化，以克服焊缝相对于母材的FCG阻力。结果还表明，压缩残余应力的影响在低R值下更为明显，并通过K _max参数发生。