基于试验数据的焊缝试样C^＊参量估算

METHODS OF ESTIMATING C^＊ PARAMETER BASED ON EXPERIMENTAL DATA FOR WELD SEAM SPECIMENS

针对焊缝和母材蠕变性能不相同的带焊缝CT试样，提出了一个等效均质材料模型，建立了焊缝中心裂纹、焊缝界面裂纹和非对称焊缝裂纹情况下由试验数据确定C^＊参量的修正式。采用ABAQUS软件进行了带焊缝CT试样，参量的有限元分析。有限元数值解与修正式的预测值比较表明：与均质材料CT试样相比，低匹配焊缝会导致CT试样的ηw因子增大，高匹配焊缝会导致ηw因子值降低，采用ASTM E1457提供的公式在低匹配情况下会过低估算C^＊参量，在高匹配情况下会过高估算C^＊参量。无论是低匹配（M＜1）焊缝还是高匹配（M〉1）焊缝，修正后CT试样的C^＊参量计算式都可给出与有限元解非常接近的估算结果，可用于焊缝蠕变裂纹行为预测。

An equivalent homogenous model is presented for the compact tension （CT） specimen with different creep properties in the weld and base metals. Based on the proposed equivalent material model, the modified experimental C^＊ integral estimation equations are derived for the CT specimens with a weld centre crack, a fusion line crack and an asymmetric crack, respectively. And then, finite element （FE） analyses for C^＊ integral of welded CT specimens are performed by using the ABAQUS software. The C^＊ parameters from FE simulation and the modified estimation equations are compared. Results indicated that an under-mismatched weld will increase the non-dimensional factor ηw while an over-mismatched weld will decrease the ηw value compared with the η0 factor of homogeneous CT specimens. It implicates that the current C^＊ estimation equation in ASTM E1457 may underestimate C^＊ for an under-mismatched weld but slightly overestimate it for an over-mismatched weld. Whether for under-mismatched weld （M〈1） or for over-mismatched weld （M〉1） considered herein, the predicted C^＊ parameters from the presented formulae are very close to FE results and thus can be used to interpret the creep crack growth of weldments .