基于结构应力法的环焊结构S-N曲线分析

S-N curve analysis of ring welding based on structural stress method

工程上多采用△F-N曲线来预测环焊的疲劳寿命,但耗时费力且不具普适性,为改进上述不足,提出了一种环焊试件疲劳寿命评估的S-N曲线.采用多种试件进行拉剪疲劳试验得到疲劳寿命,利用壳单元、梁单元以及刚性rigid单元建立环焊有限元模型,根据结构应力法计算拉剪载荷下环焊结构应力,以焊核处的应力范围△σs为纵坐标,试验寿命N为横坐标,采用两参数对数模型,以最小二乘法对疲劳数据线性拟合得到环焊疲劳寿命评估的S-N曲线方程.结果表明,数据点大都位于5倍寿命范围内,其预测寿命较为接近试验真实寿命,能够为环焊结构的寿命预测提供一定的参考.

In engineering,△F-N curves are used to predict the fatigue life of ring welding,which is timeconsuming,laborious and not universal.To improve the above inadequacies,an S-N curve for evaluating the fatigue life of the ring welding specimen was proposed.The fatigue life was obtained by tensile shear fatigue test with different ring welding specimens.The finite element model of ring welding structure was established by shell elements,beam elements and rigid elements,and the stress of ring welding structure under tensile shear load was calculated according to structural stressmethod. The S-N curve equation for fatigue life assessment ofring welding was obtained by linear fitting of fatigue data usingtwo-parameter logarithmic model with the stress range △σs ofnugget as the ordinate and the test life N as the abscissa. Theresults show that the data points were mostly within 5 times ofthe dispersed zone of life, and the predicted life was close tothe real test life, which provided a reference for the lifeprediction of ring welding structures.