基于等效原场应力的失效评定曲线

FAILURE ASSESSMENT CURVES BASED ON THE EFFECTIVE REMOTE STRESS

首先针对油气管道的断裂数据,阐述R6的选择2曲线因使用假设h(n)h(n=1)≈1带来的不足,通过分析说明该假设不但会使评定结果出现保守情况,而且可能使评定结果出现非保守情况。然后根据计算J积分的等效原场应力方法推导基于等效原场应力的失效评定曲线。文中推导的基于等效原场应力的失效评定曲线形式上类似于R6的选择2曲线,但评定精度接近基于严格J积分定义的失效评定曲线。同时,该评定曲线同样适用于任意应力应变关系材料,包括Ramborg-Osgood(R-O)关系材料和任意单调加载非R-O关系材料,例如长屈服平台钢,在工程上十分适用。

According to the analysis of the fracture data of oil and gas pipeline, the deviation of the option 2 FAC（failure assessment curve） of R6 for using the hypothesis of h（ n）/h（ n = 1） ≈ 1 is demonstrated, and because of the hypothesis, the result of assessment would be non-conservatism. Then based on the J integral calculation method of the effective remote stress, a new failure assessment curve is obtained. The new failure assessment curve is as simple as the R6 option 2, but the result of the new failure assessment curve is as accurate as the result of the curve based strictly J integral. Moreover, the new curve could be used for any stress-strain relationship material, including Ramborg-Osgood（R-O） material and non-R-O materials under monotonic increasing loading, such as long plastic yield plateau steel.