EH36钢焊接接头焊趾处应力集中对高低周复合疲劳的影响

Effect of stress concentration at weld toes on combined high and low cyclefatigue of EH36 steel welded joints

为研究船舶结构用钢EH36钢焊接接头焊趾处应力集中对高低周复合疲劳的影响,对不同焊缝形貌20 mm厚EH36钢双面全熔透对接接头进行高低周复合疲劳试验.研究发现,高低周复合疲劳对接头寿命的降低幅度随着高周应力比的增大而增大;结合数字图像相关法测量结果分析,发现焊趾处应力集中系数越大,接头的高低周复合疲劳寿命越低,其降低幅度随着高周应力比的增大而增大.基于试验数据对模型进行验证,结果表明,应力集中系数高的接头疲劳寿命低且寿命预测结果分散性增大;Palmgren-Miner模型和Zhu模型由于未充分考虑高低周耦合损伤作用,导致寿命预测结果相对危险.修正后Zhu模型在充分考虑低周疲劳对高低周复合疲劳寿命的影响后,预测寿命大于实际寿命的预测点较少,预测结果相对安全,且分散性较小,误差也较小.

In order to study the effect of stress concentration at the weld toes on combined high and low cycle fatigue(CCF)of EH36 steel welded joints for ship structure,CCF tests were carried out on EH36 steel double-sided butt joints with 20 mm thick and different weld profiles.The results show the extent of reduction in joint life subjected to CCF increased with increasing high stress ratio of high cycle fatigue;Based on the digital image correlation method,the higher the stress concentration coefficient at the weld toes,the lower the CCF life of the joints.The extent of reduction increased with increasing stress ratio of high cycle fatigue.Validation of the models based on experimental data shows that joints with high stress concentration coefficient have lower fatigue life and increased dispersion of life prediction results;The Palmgren-Miner model and Zhu model do not fully consider the CCF damage effect,which leads to dangerous prediction results of CCF life.The modified Zhu model fully considers the influence of CCF.There are few prediction data points that the predicted life is higher than the actual life.The prediction results are relatively safer.The dispersion and the error are smaller.