基于热点应力法的焊接结构疲劳评估

针对传统名义应力整体法在焊接板结构疲劳分析应用中的实际困难,介绍和分析了应用于海洋结构工程领域的基于表面外推的热点应力法.通过对焊接样件在不同应力水平下的疲劳试验,获取了焊接样件在97.7%可靠度下的疲劳寿命.采用热点应力法计算样件焊趾处热点应力值,提出考虑主板厚度效应的修正S-N曲线,并预测了样件的疲劳寿命.结果表明:板厚修正后的热点应力S-N曲线应用于薄板焊接结构疲劳寿命评估具有更高的精度和可靠性.以轨道车辆用焊接天线梁为例,采用该方法分析了焊缝处的热点应力,其最大应力发生位置与线路运用中出现裂纹位置相吻合,其计算寿命为7.1×10~5次,与实际运营结果基本一致.为平板焊接接头的抗疲劳设计提供参考.

Fatigue assessment of weld structure based on the hot spot stress method

In view of the practical difficulies facing the traditional nominal stress approach applied in fa-tigue analysis of weld plate structure,the hot spot stress method based on the surface extrapolation is in-troduced comprehensively.It has been developed in marine structural engineering well.The specimens are loaded under different stress levels and the fatigue life with 97.7％ reliability is obtained.The hot spot stress of the specimen weld toe is calculated by the spot stress method and the fatigue life is given by FAT 90 modified S-N curve considering the plate thickness effect.The results show good accuracy and better reliability in the assessment of weld structure fatigue life.Taking the railway antenna beam as ex-ample,the hot spot stress method is used to get the maximum stress point,which is consistent with the fatigue crack position in service.The fatigue life prediction of the antenna is 7.1 ×105 and it coincides with the actual operation life basically.The analysis method can be applied on the anti-fatigue design of weld joints of plate structure.