Astroloy合金中弯曲晶界显著改善了材料的蠕变持久塑性和蠕变裂纹生长抗力。通过尖切口根处蠕变裂纹形成寿命分析与试验比较,证实蠕变J~*积分是控制尖切口(和裂纹)场的有效参量。据此由线性损伤模型和HRR奇异性结合,导出与直晶和弯晶试验结果吻合良好的蠕变裂纹扩展速率表达式: da/dt=Be~(k/n+1)D(x_0)J~(*kn/n+1) 从晶界孔洞形成角度讨论了弯曲晶界蠕变损伤的微观机制。
By comparing the measurement and the prediction of the creep crack initiation life at the sharp notch root, it is demonstrated that the creep J~*-integral is the effective parameter controlling the asymptotic field at the tip of the notch (and so the crack). Accordingly, a combined analysis on the linear damage model and the HRR singularity is carried out and an expression for the creep crack growth rate is derived as:da/dt=Ba k/n+1 D(x_0)J~* kn/n+1which is in good agreement with the experimental results of material with smooth and wavy grain boundaries. A microscopic mechanism of the creep damage in the material with the wavy grain boundaries has been discussed from the view point of the cavity formation along the grain boundary.
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