铝合金熔焊气孔与裂纹交互作用模拟

为研究铝合金熔焊接头中裂纹与气孔交互作用对接头疲劳行为的影响，基于杂交多边形有限单元法（hybrid polygonal element，HPE），构造了单独含椭圆洞和裂纹的多边形单元格式，建立了同时含裂纹和气孔的激光-电弧复合焊接铝合金接头的平面应力模型，研究了气孔的分布对焊根裂纹尖端场的影响.研究结果表明:在较为稀疏的网格模型下，HPE法数值解误差可控制在0.5%以内；焊缝下部的小气孔使得裂纹尖端标准化Ⅰ型和Ⅱ型应力强度因子分别增大2.15%和324%，增强效应明显，并且气孔与裂纹间距离越近，两者耦合作用愈强. 

Simulation of Interactions between Pores and Cracks inside Fusion Welded Aluminum Alloys

In order to investigate the influence of interactions between cracks and pores within fusion welded aluminum alloys on the performance of the joints, polygonal elements each embedded with a single elliptical hole or multi cracks were constructed based on the hybrid polygonal element (HPE). Then, a plane stress model was formulated for a fusion welded aluminum alloy joint, which consisted of both a main crack and arbitrarily distributed pores, and the influences of the distribution of these pores on the cracks initiated from the weld root were studied. The result shows that errors between the HPE method solutions and the theoretical ones can be limited to the level of 0.5%, even if sparse meshes are used. Smaller-sized pores in the bottom of the welding joint can increase the stress intensity factor (SIF)Ⅰand SIFⅡby 2.15% and 324%, respectively, showing a significant enhancement effect on the stress field of the crack tip; what's more, the smaller the distance between pores and cracks, the greater the coupling effect.