纳入拘束效应的焊接接头蠕变裂纹扩展速率预测方法

Creep Crack Growth Rate Prediction Method for Welded Joints Considering Constraint Effect

高温焊接结构的蠕变裂纹扩展(Creep crack growth, CCG)是影响含缺陷焊接结构可靠性的重要因素。以P92钢焊接接头为对象,设计热影响区(Heat affected zone, HAZ)中心裂纹和HAZ/母材(Base metal, BM)界面裂纹模型的多种材料蠕变性能失配组合,研究蠕变性能不匹配对裂纹尖端拘束水平Q_(M)*以及CCG的影响机制。研究表明,对于HAZ中心裂纹,若周围的蠕变软材料受到裂尖的蠕变硬材料拘束,可能出现二次裂纹;若HAZ和BM的蠕变强度不变,增加焊缝(Weldingmetal,WM)的蠕变强度,仍会使BM的损伤增加。对于HAZ界面裂纹,若界面的蠕变软材料受到蠕变硬材料拘束,仍可能形成二次裂纹,但形成二次裂纹的倾向变弱。无论是HAZ中心裂纹还是界面裂纹,较窄的HAZ宽度会加剧失配效应。提出基于C*-Q_(M)*的材料蠕变性能失配下焊接接头CCG预测方法,并利用试验结果验证纳入拘束效应的CCG预测方法的准确性。该方法解决不同蠕变性能失配程度的焊接构件CCG速率的精准评估难题。

Creep crack growth(CCG)of high temperature welded components can affect the reliability of welded structures containing defects.For P92 steel welded joints,two sets of material configurations of the HAZ center crack and HAZ/BM crack model are designed,and the influence mechanism of creep properties mismatch on crack tip constraint Q_(M)* and CCG are studied.The result show that in terms of the HAZ center cracks,secondary cracks may occur if the surrounding creep soft material is constrained by the creep hard material at the crack tip;increasing the creep strength of WM still cause the more severe creep damage of BM if the creep strength of HAZ and BM remain unchanged.For HAZ interface cracks,secondary crack may form if the creep soft material at the interface is constrained by the creep hard material,but the tendency to form secondary cracks is weaker.Whether a central HAZ crack or an interfacial crack,a narrower HAZ width presented a stronger mismatch effect.The CCG prediction method based on C*-Q_(M)* for creep properties mismatched welded joints is established,and the accuracy of CCG prediction method incorporating constraint effect is verified by the experiment results.This method can solve the accurate prediction for the CCG rate of welded components with different creep properties mismatch degrees.