基于缺口应力法的IIW多轴疲劳准则分析

Research on IIW multiaxial fatigue criterion based on notch stress approach

焊接接头的多轴疲劳强度评估是领域内的复杂课题.结合缺口应力法,利用IIW多轴疲劳准则对已公开发表的文献中的多轴疲劳试验数据进行了重新评估.结果表明,缺口应力系统下的比例加载与非比例加载数据点重合性较好;IIW推荐的单轴疲劳评估S-N曲线不适用于多轴疲劳评估,循环次数在1×10^4~1×10^5范围内时,可能得到偏危险的评估结果;而高于1×10^5次时,评估结果过于保守.基于此,拟合得到了存活率Ps=97.7%的S-N评估曲线,其疲劳等级FAT=430MPa,斜率M=5.8,同时适用于比例加载与非比例加载,可为工程焊接结构疲劳寿命预估提供参考.

Multiaxial fatigue strength evaluation of welded joints is a complex subject for engineering.Based on IIW multiaxial criterion,experimental data from published literatures were re-evaluated using notch stress approach.The results reveal that the uniaxial fatigue assessment S-N curve recommended by IIW is unfit for multiaxial fatigue.Whereas,the data points of proportional loading and non-proportional loading have good coincidence under notched stress system.The assessment result is dangerous when the number of cycles is in the range of 1 × 10^4 ~ 1 × 10^5,and it is too conservative over 1 × 10^5 times.Based on this,the S-N curve (FAT=430 MPa,m=5.8) with the probability of survival Ps=97.7% is proposed for both proportional and non-proportional loading.This work can provide useful references for fatigue life prediction of engineering welded structures.