在630℃下,对P92钢进行应力控制下的蠕变-疲劳交互作用实验,研究P92钢高温蠕变-疲劳交互作用下的裂纹扩展行为,并结合断口形貌分析蠕变-疲劳裂纹扩展的机理以及α-N曲线的转折点含义.结果表明:P92钢在蠕变-疲劳交互作用下的断裂属于蠕变韧性断裂,应该用(Ct)a.作为裂纹扩展的断裂参量;P92钢在蠕变-疲劳交互条件下,试样的断口主要表现为蠕变孔洞以及微裂纹.此外,发现a-lg(Ni/Nf)曲线以及(da-dN)-N曲线中的拐点,分别对应蠕变-疲劳裂纹萌生区向扩展区转变周次以及扩展区向瞬断区转变的周次.
Creep-fatigue interaction tests of P92 steel at 630℃ under stress-controlled were carried out,and the crack propagation behaviour of P92 steel was studied.The fracture mechanism of crack growth under creep-fatigue interaction and the transition points in a-N curves were analyzed based on the fracture morphology.The results show that the fracture of P92 steel under creep-fatigue interaction is creep ductile fracture and the (Ct)avg parameter is employed to demonstrate the crack growth behaviour;in addition,the fracture morphology shows that the crack growth for P92 steel under creep-fatigue interaction is mainly caused by the nucleation and growth of the creep voids and microcracks.Furthermore,the transition point of a-lg(Ni/Nf) curve corresponds to the turning point of initial crack growth changed into steady crack growth while the transition point of (da/dN)-N curve exhibits the turning point of steady creep crack growth changed into the accelerated crack growth.
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