Research On The FLD And Uniaxial Tensile Behaviour Of5A02Aluminium Alloy Sheet In The Electromagnetic Pulse Forming

Electromagnetic pulse forming (EMF) is a new type of technology which issuitable for sheet and tube metal manufacturing. Sheet metal shows significantformability during processing because of the high strain rate. In this article, we use5A02aluminum alloy sheet metal as the object. The Forming Limit Diagrams (FLD)of quasi-static and electromagnetic pulse processing are respectively establishedthrough the Rigid Punch Bulging Test and the Electromagnetic Pulse Bulging Test.And the Johnson-Cook model is established through the quasi-static tensile test andthe high speed tensile test. Also, we set up two kinds of sheet metal high speedtensile tests and carry out numerical simulation and processing experiment, whichare electromagnetic pulse straight tensile test and electromagnetic pulse bulgingtensile test.We can get two conclusions by comparing the two FLDs. The electromagneticpulse processing FLD is much higher than the quasi-static FLD. The ultimate strainis increased by30%~40%in the uniaxial tensile state, and doubled in the equiaxialtensile state.In this article, the Johnson-Cook model is an accurate model for the numericalsimulation which is established through the quasi-static tensile test and the SplitHopkinson Tensile Bar (SPTB).We set up a device which can conduct the high-speed tensile test. The strainrate can be set from20s-1to3267s-1, or even higher. The strain rate is controlled byregulating the discharge energy.From the numerical results we can get some conclusions. The strain rate isincreasing with the improvement of the capacitor and the voltage in theelectromagnetic pulse tensile test. In the early deformation of the sheet metal, stresswave propagate along the specimen. Deformation of the specimen is more uniformbecause of the transmission, reflection and interference of the stress wave.Distribution of stress in the electromagnetic pulse bulging tensile test is nonuniform.The ends of the scale distance suffer the maximum stress and strain, and the fractureoccurs at this place. The stress and strain are smaller relatively at the center of thescale distance.We come to conclusions after the processing experiment of the electromagneticpulse tensile test and the bulging tensile test, that elongations of the specimens aremuch higher than the quasi-static tensile test, increasing by13%~53%. Theelongation increases with the strain rate and the strain of the specimen is uniform inthe electromagnetic pulse tensile test. The strain rate of the specimen is higher than 1500s-1in the electromagnetic pulse bulging tensile test, and the deformationprocess is very consistent with the simulation result.In this article, we also analyze the fracture mode of the sheet metal afterdifferent tensile test with the scanning electron microscopy. Conclusion is that thefracture model is dimple fracture at either low speed tensile or high speed tensile.As the strain rate increases, more intensive dimples distributed evenly along thefracture, showing excellent ability of plastic deformation. Metal around the fractureis melt because of the eddy current effect in the electromagnetic pulse bulgingtensile test.