双轴载荷下失效评定图的研究

A STUDY OF FAILURE ASSESSMENT DIAGRAM (FAD) UNDER BIAXIAL LOADING

本文通过双轴载荷下的断裂试验和理论分析研完了16MnR钢所制成的含中心穿透裂纹的十字形板试样的断裂性能,并分别对英国中央电力局的CEGB R_6法和美国电力研究所EPRI工程估算方法的失效评定进行了双轴载荷效应的修正,作出了双轴载荷下估算含缺陷结构安全裕度的失效评定图(FAD)。试验结果表明,在不同的双轴载荷比下启裂的J积分J_i比较接近,而J控制裂纹扩展条件的J_R曲线受不同的双轴载荷比影响较显著。在几种评定方法的比较中,认为经双轴载荷修正的EPRI失效评定图与实验结果吻合得较好。

A fracture experiment under biaxial loading and theoretical analysis were conducted to study the fracture behaviour of cruciform specimen, made of 16MnR steel with a central penetrated crack, and the modified method of failure assessment of CEGB R6 and of EPRI Engineering Approach for biaxial loading have been proposed respectively in the present work. On the basis of these research works,the Failure Assessment Diagram(FAD)for evaluating the safety margin of cracked structure under biaxial loading has been plotted.The experimental results revealed that the J-integrals based on the measured instantaneous load of initiation of crack growth, J_1 under different ratio of biaxial load were almost identical, while the J_R curve of J-integral based on the controlling conditions of crack propagation was affected by different ratio of biaxial load. In comparison, it was found that the modified Failure Assessment Diagram of EPRI method for biaxial loading proposed agreed with the experimental results better than the others.