拉-剪应力场下全熔透十字型焊接节点疲劳寿命评估

Fatigue Life Assessment of Full-Penetration Cruciform Welded Joints under Tensile Shear Cyclic Stress

为研究全熔透十字型焊接节点在拉-剪应力场反复作用下的疲劳损伤累积规律及疲劳寿命预测方法,选择不同倾角(0°、15°、30°、45°)全熔透承载焊缝十字形焊接节点,构建不同比例的拉-剪应力场.利用ANSYS建立有限元模型,对不同倾角下全熔透十字形焊接节点的应力分布状态及应力集中系数进行比较分析.完成4组12个比例加载时正应力和剪应力共同作用下的焊接节点疲劳试验.基于名义应力分别采用等效应力法、相互作用方程法和双参数临界面法,对全熔透十字形焊接节点疲劳寿命进行评估,并与试验结果进行对比分析.研究结果表明,应力比大于0.5时,按国际焊接学会方法及Eurocode方法得到的疲劳寿命偏大,主拉应力法得到的疲劳寿命仅为试验结果的1/3,双参数临界面法和等效应力法得到的疲劳寿命与疲劳实验结果吻合较好.

To investigate the fatigue performance and fatigue life assessment method of full-penetration welded joints in tensile shear cyclic stress, fatigue tests and finite element analyses were carried out. With different inclined angles of weld lines of 0 ° , 1 5 ° , 3 0 ° , and 4 5 ° , full-penetration cruciform welded joints were designed at different tensile shear stress ratios. Using the ANSYS finite element program, three-dimensional （3D） finite element models of cruciform welded joints were developed and the stress distributions and stress concentration factors were investigated. Four groups of fatigue tests （12 specimens） were conducted under proportional loading over the same stress range as that on the end of the steel plates. Based on the nominal stresses, the fatigue lives of full penetration cruciform welded joints were evaluated by using effective stress, interaction equations, and bi-parametrical critical plane approaches. The accuracy and reliability of the assessment methods were checked against the experimental results of the fatigue testing. The research results showed that the fatigue life calculated using the approach of the International Institute of Welding （IIW） and Eurocode is longer than the test result, whereas the fatigue life based on the principal-tensile-stress method is shorter thanthe test result. Furthermore, fatigue life given by the effective stress and bi-parametrical critical plane approaches are in good agreement with the test results.