Research On Self-Piercing Riveting With Half-Hollow Rivet For Hybrid Metals Based On Numerical Simulation

Multi-material body structure is an inevitable trend of lightweight body. In oder to solvethe jointabiltiy of hybrid metals which spot-weld could not do effectively, we tookself-piercing riveting with half-hollow rivet(HSPR) as the operation and researched the fea-sibility of riveting and joint performance. Details listed below:1. Choosing appropriate size and shape half-hollow rivet and die according to sheets’thickness and strength.2. Studying the dynamic mechanical behaviors and coming to the dynamic constitutiveequations of lightweight materials.3. Researching the impact on joint quality of the matches of rivet/sheets strengththrough numerical analysis method.4. Analyzing how the speed of riveting impacts the quality of the joint.5. With a single joint for the study, getting the anti-pull strength of joint and derivingthe principle of multi-joint pitch.First, we made the thickness of sheets cleared, and then made sure the size of rivet anddie according to the thickness of sheets.In the paper, we introduced Split Hopkinson Pressure Bar(SHPB) test which researchesthe mechanical behavior specialized in medium and high strain rates. Here, we got severalstress to strain curves and J-C constitutive equations, which characterized by the effect ofstrain hardening and strain rate hardening, which can be used in the analysis of HSPR joint.Matching of rivet to sheets strength is a key affect the quality of the joint. For example,the rivet will pierce the bottom sheet if the strength of rivet is much higher than sheets’. Onthe contrary, the rivet even cannot pierce the top sheet to form an effective interlock betweentop and bottom sheets at all if the strength of rivet is much lower than sheets’. So we pointed the strength ratio of rivet to sheets must be within a certain range in order to form an effec-tive mechanical interlock between the top and bottom sheet.The speed of riveting does not only play an important role on the efficiency of assembly,but also the quality of jiont by the way of how strain rate influence the behaviors of plastichardening and failure strain. The studies show that the increase in strain rate led to the in-crease in plastic hardening and the decrease in failure strain, combined effect of which affectthe quality of joint. In this paper, we found that the sheets rupturing and rivet hardening pre-maturely if the speed of riveting is too fast, and the efficiency of assembly will be decreasedif the speed is too slow, even the quality of joint is perfect. Therefore, the speed of rivet mustbe balanced between assembly efficiency and riveting quality.The key HSPR could be used largely is determined by joint pitch, too. In this paper, theanti-pull strength of a single joint was put forward and a set of factors influence HSPR jointpitches were proposed based on the joint’s strength equal to sheet’s per unit area. The com-paration of joint pitch between HSPR and spot-weld come to the conclusion that the HSPRjoint pitch is larger than spot-weld joint pitch. That is to say, it is more economic and practi-cal if we take use of HSPR rather than spot-weld when connecting hybrid sheets.