考虑形状比的焊趾裂纹扩展行为的数值仿真分析

针对焊趾处初始裂纹的不同形状比，基于NASGRO裂纹扩展速率模型对裂纹扩展过程进行了数值仿真. 以具有不同形状比的半椭圆表征焊趾表面裂纹，考虑短裂纹扩展阶段，采用M积分计算整个裂纹前沿的应力强度因子，并将裂纹前沿应力强度因子中值点作为裂纹扩展的主要控制参量，模拟并分析了不同形状比条件下裂纹前沿的形状演变和应力强度因子的分布及变化特点. 结果表明，随着裂纹的扩展，短裂纹阶段的不同形状比变化将趋于一致；短裂纹的形状比对早期裂纹扩展有较大影响，并最终导致整体疲劳寿命的显著差异性；综合初始形状比对裂纹前沿应力强度因子、扩展形状以及疲劳寿命的影响，可将其作用效果的强弱拐点作为界定短裂纹与长裂纹的有效参考. 开展了十字焊接接头疲劳验证试验，试验结果与仿真结果具有较好的一致性.

Numerical simulation analysis of crack propagation in weld toe considering aspect ratio

In terms of the different aspect ratio of initial crack in weld toe, the numerical simulation of crack propagation was carried out based on the NASGRO crack growth rate model. Semi-ellipsoid with different aspect ratio was used to characterize the surface crack of weld toe. Considering the short crack propagation stage, M integration was used to calculate the stress intensity factor of the whole crack front and the median value of crack front stress intensity factor was taken as the main control parameter for crack propagation. The shape evolution stress intensity factor distribution and change of crack front were simulated and analyzed under different aspect ratio. The results show that with propagation of the crack, the different shape of the short crack tend to be more consistent; The shapes of the short cracks have a greater influence on the early crack propagation and eventually lead to significant differences in the overall fatigue life; Based on the influence of the initial aspect ratio on the stress intensity factor, the extended shape, the fatigue life of the crack front, and the inflection point of its effect can be used as an effective reference to define the short crack and the long crack. The fatigue test of cross welded joint was carried out. The test results show good agreement with and simulation results.