Research On Riveting Process And Performance Of Sandwich Structures Self-piercing Riveted Joints

With the need for lightweight development of automobiles,the new sheet material connection technology-self-piercing riveting technology is being widely used in various industrial fields.In order to explore the application of self-piercing riveting technology in the form of "sandwich structure",several study and work were carried out in the paper:1.A variety of panel materials and a variety of core material combinations of sandwich structure laps can be connected availably using the technology of self-piercing riveting,and the forming quality of the joints is qualified.The optimal parameters of riveting process that meet the quality requirements of each group of SPR joints were obtained.The quality of the cross-section of each joint was measured according to the SPR joints assessment criteria: head height,rivet spread and remain bottom thickness.The use of online quality monitoring system ensures the coherence of the quality of the joints,providing a guarantee for follow-up research.2.In terms of static strength study of sandwich self-piercing riveted joints.The static tensile-shear test was utilized to obtain the F-s curves of the joints of each group,and the validity of the data obtained from the experiment was verified.Based on this data,the static average maximum dead load and average mechanical energy absorption of the joints were calculated.Combined with the failure modes and fracture morphology of each joint,the influence of the core material on the static strength of the self-piercing riveted joint was carried out.3.In terms of the dynamic strength of sandwich self-piercing riveted joints.The fatigue and fatigue cycle data of each joint were obtained under a multi-stage load level utilizing fatigue tests of single tensile-tensile modes.The fatigue data of all joints were fitted by the stress amplitude-life curve fitting method.The result was more accurate.Than compared the fatigue performance of the joints by using the fitted F-lgN curve,combined with the fatigue failure modes of each joint.The results show that,compared with the performance of the substrate material,the addition of the core material has a limited increase in the fatigue strength of the joint.However,a further microscopic analysis shows that the addition of carbon fiber reduces the oxidation of the material caused by the relative motion of the rivets and the rivets on the inner wall of the lower plate,and reduces the negative influence of fretting wear on the joint fatigue strength.