基于八节点二次壳单元的等效结构应力法

Equivalent structural stress method based on eight-node second-order shell element

基于八节点二次壳单元的节点力和节点力矩,导出了焊趾截面上的分布线力与分布线力矩,进而分别针对闭合焊缝和非闭合焊缝对线力和线力矩进行了单元集成.以T型焊接接头为研究对象,验证了基于八节点二次壳单元的焊趾结构应力对单元类型与网格尺寸的不敏感性,并根据已有结果验证了其有效性.对RHS管接头T型焊缝两条焊趾的结构应力进行了计算,发现若圆弧拐角处的网格过于稀疏将引起单元中间节点的结构应力产生较大波动,该问题可以通过网格加密得以解决;利用等效结构应力与主S-N曲线,对RHS管接头的疲劳失效位置与疲劳寿命进行了预测,数值结果与实验测试数据基本吻合.

Based on the nodal force and nodal torque of the eight-node second-order shell element,the distributed line force and line moment on the section of weld toe are derived,and then the integrated forms of line force and line moment are obtained for the closure and non-closure welds.By modeling a T-welded joint,it is shown that the structural stress based on eight-node second-order shell element is insensitive to the element type and mesh size,which is validated by the available results.The distributions of structural stresses along two weld toes of a rectangular hollow section joint （RHS） are calculated.It is found that the structural stress on the middle node of the second-order shell element exhibits greater fluctuation if the mesh modeling the 90° corner region is too sparse,which can be solved by using finer mesh.With the equivalent structural stress and the master S-N curve,the fatigue failure position and fatigue life of the RHS joint are predicted,and the numerical results agree with the experimental data very well.