腐蚀环境下自冲铆接头竞争失效机制及力学性能分析

Analysis of competitive failure mechanisms and mechanical properties of self-piercing riveted joints in corrosive environments

为研究腐蚀环境下自冲铆接头失效模式的转变机理和力学性能特征,采用0.6 mol/L的NaCl溶液对多组自冲铆接头进行周浸腐蚀试验,通过力学测试和扫描电子显微镜对接头的力学性能及失效模式进行分析.结果表明,异质接头的失效模式随腐蚀周期延长由Ⅰ向Ⅲ转变,转变速率取决于接头材质,同质接头的失效模式不受腐蚀周期的影响.短期腐蚀下,搭接区板间腐蚀产物使得同质和异质接头失效载荷均有所上升;异质接头上升幅度较大,腐蚀后期其失效载荷较同质接头损失严重.异质接头稳定性较差,凸模制备的同质组合接头较平模稳定性好.异质接头电化学腐蚀剧烈,下板铆接点底部材料的脱落由应力集中所产生的撕裂纹所致.

In order to study the transition mechanism and mechanical properties of the failure mode of self-piercing riveted joints in corrosive environment, the 0.6 mol/L NaCl solution was used to carry out the immersion corrosion test on several groups of self-piercing riveted joints. Mechanical properties and failure modes of joints are analyzed by mechanical testing and scanning electron microscopy. The results show that the failure mode of heterogeneous joints changes from Ⅰ to Ⅲ with the prolongation of corrosion cycle, and the transformation rate depends on the joint material, while the failure mode of homogeneous joints is not affected by the corrosion cycle. Under short-term corrosion, the inter-plate corrosion products of self-piercing riveted joints increase the failure load of both homogeneous and heterogeneous joints, the failure load of heterogeneous joints varies widely throughout the corrosion cycle. Heterogeneous joints are less stable, and homogeneous combination joints prepared by convex dies are more stable than flat dies. Heterogeneous joint electrochemical corrosion is intense, self-piercing riveted joints bottom material off by the stress concentration generated by the tear lines.