Effect of material combinations on mechanical properties of flat bottom riveted joint

Flat bottom riveting is a newly developed joining technique. Since the bottom surface of joint is flat, the joint can be applied in areas that need a high degree of smoothness. This article investigated the effect of material combinations on mechanical properties of joints. Four material combinations which involved two kinds of aluminum alloy were produced. Cross sections of joints were observed by metallographic microscope and geometrical parameters of joints were measured. It was found that material combinations exerted significant influence on the geometrical parameters of joints. When the bottom sheet remained the same, with the increase of top sheet hardness, the interlock thickness of joint decreased, while the neck thickness of joint increased. Tensile and shearing tests were conducted on joint to obtain the tensile load and the shearing load of joint. The absorbed energy of joint in shearing test was calculated. Results showed that when joining materials with different hardness values, the joint with high hardness sheet on the top exhibited higher static load than the joint with high hardness sheet on the bottom. In tensile tests, 1060–5052 joint failed in the manner of neck fracture, while other joints failed in the manner of button separation. In shearing tests, 5052–1060 joint failed in the manner of button separation, while other joints failed in the manner of neck fracture.