复杂应力场下T型管节点应力强度因子计算和分析

Calculation of the stress intensity factor in complex stress field based on weight function

疲劳破坏是船舶及海洋工程结构物失效的主要原因之一.海洋结构物大型焊接结构一般处在复杂的应力应变场中,而应力强度因子是基于断裂力学预报疲劳寿命方法的关键参数.因此如何计算复杂应力场中的应力强度因子,以便预测焊接结构的疲劳寿命是当前研究的主要趋势.文中提出了一种有限元与权函数相结合的方法求解复杂应力场下海洋平台T型管节点的应力强度因子,并基于该方法,分别对轴向载荷、面内外弯曲载荷和组合载荷作用下T型管节点的应力强度因子变化趋势做了分析,采用单一裂纹扩展率曲线模型对T型管节点的疲劳寿命进行了预报.结果表明:通过与手册公式的计算结果比较,该方法计算得到的疲劳寿命偏小,更有利于对寿命的保守估计;减少了求解裂纹应力强度因子的难度,提高了效率,使得求解复杂应力场下的应力强度因子简单可行.

Fatigue failure is one of the main reasons for the failure of the ship and marine engineering structures.Marine structures are generally in a complex stress and strain field,and stress intensity factor is a key parameter for predicting fatigue life based on fracture mechanics. So,calculating the stress intensity factor in the complex stress field to predict the fatigue life of welded structure is the main trend of the current research. This paper proposed a weight function combined with the finite element method to calculate stress intensity factor of T-type tubular joints in complex stress field. Based on this method,we analyzed the stress intensity factors of T-type tubular joints under axial load,internal and external bending loads and combined loads separately,and the fatigue life of the T tube joints is predicted by using the single crack growth rate curve model. The results show that the fatigue life obtained by the method is smaller than that obtained by the manual formula by comparison of the results of calculation,and it is more conservative estimation of the life. The method proposed in this paper can reduce the difficulty of calculation of the stress intensity factor and improve the efficiency. It is simple and feasible to calculate the stress intensity factor for the case of acomplex stress field.