Numerical Simulation And Experimental Research Of TB3 Rivet In Electromagnetic Riveting

Electromagnetic riveting (EMR) is a new kind of riveting technology which transforms the electromagnetic energy to the mechanical energy. EMR has characteristics of high loading rate and process quality consistency, which contributes to form hard deformation material by one shot. EMR is one of the most effective processes to realize the joining of titanium alloy and composite structure, which is used widely in aircraft manufacturing. In this paper, the deformation behavior in EMR of TB3 rivet was investigated from macro and micro scales by the combining methods of numerical simulation and experimental study.The stress strain curves of TB3 material under different deformation conditions were obtained through Hopkinson pressure bar tests and quasi-static compression tests. The Johnson-Cook constitutive model of thermoviscoplastic was established, and microstructure analysis of the samples under different deformation conditions was done. The results show that TB3 was the sensitive material of strain rate and temperature. Flow stress increased with strain rate increasing and decreased with temperature increasing.Based on the established constitutive equation, the deformation of TB3 rivet in electromagnetic riveting was conducted using ANSYS-LS-DYNA by numerical simulation. The dynamic deformation and adiabatic temperature rise of rivet were analyzed. The effect of loading rate and different die forms on rivet deformation was investigated. The results showed that the rivet deformation composed of the whole free upsetting and the local free upsetting. The distribution of the adiabatic temperature was basically same with that of the equivalent strain. Die form and loading rate had a great impact on the rivet deformation.Based on the simulation results, the effect of various parameters (die form, coil, driver, etc.) on the rivet deformation was analyzed by electromagnetic riveting process test.Then, comparison experiments between low voltage electromagnetic riveting and pressure riveting were conducted. And the riveting process parameters of titanium-to-titanium and composite material-to-composite material were achieved respectively by low voltage electromagnetic riveting joinging tests. The results show that the process parameters had an important impact on the rivet deformation. Under appropriate process parameters, low voltage electromagnetic riveting and pressure riveting can realize the joinging of titanium-to-titanium and composite material-to-composite material. And, the former forming method produced more uniform deformation and greater interference.Microscopic analysis indicated that during quasi-static pressure riveting, the slipping was the rivet deformation way, and mechanical twin played a supporting role. In low voltage electromagnetic riveting, adiabatic shearing was the main deformation way. With the deformation increasing, the width of the adiabatic shear band in rivet got narrower. Dynamic recrystallization and the phase transformation did not occur in the the shear zone and the only deformation band was observed.