Research On Deformation Behavior Of DP600 High Strength Steel With Magnetic Pluse Driving Forming

In the modern industrial and technological environment,energy and environmental protection have become an unavoidable and important social issue.For the automotive industry,lightweight is an important way to reduce energy consumption,high-intensity can improve safety performance.Therefore,there is a recent global trend in the automotive industry of increasing the use of high-strength steel sheets aiming at producing lighter and safer cars.At present,there exists some forming problems in the application of high strength steel,such as easy cracking,large deformation resistance,superfluous spring back,and so on.Magnetic pulse forming is high speed forming process,which can significantly improve the formability of metal material.This paper mainly studies the high speed rate forming of DP600 dual-phase steel sheet,which is the most widely used.According to the quasi-static tensile test and high speed dynamic tensile test with Hopkinson Tensile Bar of DP600 dual-phase steel,the stress-strain curves of quasi-static and high strain rate under different strain rates were been obtained.The mechanical property of DP600 steel under different strain rates were studied.The results showed that the yield strength and ultimate tensile strength of the materials were obviously improved and the forming properties were greatly improved.Based on the tensile test data at different strain rates,the JC constitutive model of DP600 steel was established and compared with the experimental values.The results indicated that the constitutive model could accurately describe or predict the plastic response of DP600 steel under both quasi-static and high strain rates.Based on the high speed dynamic tensile test of DP600 dual-phase steel,the influence of strain rate on the fracture morphology and microstructure was investigated by the combination of macroscopical and microscopic analysis.The microstructure evolution of dual-phase steel sheet at different strain rates was revealed.The 2D finite element model of DP600 dual-phase steel sheet of magnetic pulse forming was established by using the multi-physics coupling field finite element analysis software ANSYS.The magnetic pulse forming process of DP600 dual-phase steel plate under different discharge voltage and different thickness of aluminum alloy driving plate was analyzed.The distribution of current density,electromagnetic force and magnetic force line on the drive plate was obtained.The change rule of sheet forming profile,deformation speed and strain rate with discharge voltage and driving plate thickness was analyzed,which provided theoretical guidance for subsequent experimental research.Due to the low conductivity of high strength steel,high conductivity aluminum alloy was used as driving plate to drive the deformation of high strength steel sheet.The reasonable size of the coil,the structure of the die and the dimension of the specimen were designed on the basis of simulation.The bulge height and thickness distribution of DP600 dual phase steel sheet under different discharge voltage and driving sheet thickness were analyzed,and the forming rule and deformation behavior of high strength steel sheet magnetic pulse were explored.The results indicated that the maximum forming height had a linear relationship with the discharge voltage,and the forming performance was the best by using 2mm driver sheet and the energy utilization was the highest.