应力集中对A7N01铝合金焊接接头疲劳性能的影响

Influence of stress concentration on the fatigue properties of A7N01 aluminum alloys welded joints

采用脉冲MIG焊的方式制备了A7N01铝合金焊接接头,接头类型分别为对接、十字接、搭接等三种型式。采用A NSYS有限元仿真模拟不同类型接头的应力集中系数。研究不同类型接头疲劳S-N曲线,并分析断口微观形貌。结果表明:对接、十字接、搭接三种接头具有不同的应力集中系数,搭接接头具有最高的应力集中系数,十字接头次之,对接接头最低。随着应力集中系数的增大,三种接头的疲劳极限降低,并且在同样的加载应力下,疲劳循环周次也随着应力集中系数的增大而降低,但接头的微观断裂机理基本一致,都是在焊趾处为疲劳裂纹起源。证明应力集中不会影响A7N01铝合金焊接接头的断裂机理,由于高的应力存在,疲劳极限显著降低,因此在进行接头设计时,要考虑应力集中的影响。

A7N01 aluminum alloys welded joints were fabricated by MIG welding technology,the samples were divided into butt welded joints,cross section welded joints and lap welded joints. The stress concentration coefficient of the different welded joints was modeled by ANSYS technology. Different types of fatigue properties S-N curves were analyzed and the microstructure of fracture was analyzed too. The results showed that the lap joints had the highest stress concentration coefficient and the butt joints had the lowest.The fatigue limit decreased with the increasing of the stress concentration coefficient. The cycles decreased with the increasing of the stress concentration coefficient too under the same load. The fracture mechanism of the three joints were the same and all originated from the weld toe. It can be concluded that the stress concentration did not influence the mechanism,but the fatigue limit decreased with the high stress. Therefore must consider the stress concentration when design the welded joints.