Energy Absorption Characteristics Research Of Magnetic Pulse Bulged Circular Aluminum Tubes

Safety, energy saving and environmental protection are three major issues considered in the process of automobile research and development. As the global energy shortage and environmental pollution problem increasingly severe, how to achieve energy conservation and reduce the emissions are valued by national governments and the requirement of energy conservation and emissions reduction for cars is increasing day by day. Under this background, the automotive lightweighting become a really important topic that the auto enterprises to research and the important way that car companies deal with the increasingly stringent emissions policy. The use of lightweight materials, optimize the structure design and the use of the new forming process are three of the most important way to realize the automotive lightweighting. In the aspect of forming process, magnetic pulse shaping is one of the most widely used high speed forming method. When the metal blank is in the pulse magnetic field, the magnetic forces act on it. Magnetic pulse forming make the metal blank deform by the magnetic field force. Magnetic pulse forming technology can improve the materials forming limit and can largely reduce the springback., so the forming limit of aluminum alloy at room temperature can largely improved by using magnetic pulse forming technology. In this paper, the energy absorption characteristics of the tube after magnetic pulse bulging is studied through the axial crushing test. The results showed that the energy absorption characteristics of tubes with the same mass could vary greatly by adjusting the geometry of the tube and the amount of work hardening experienced by the tube during magnetic pulse bulging. This paper puts forward two kinds of axial crushing finite element modeling method of magnetic pulse bulging tube. One is based on the inverse technique for determining the material constitutive parameters of magnetic pulse bulging tube, another is electromagnetic-structure coupling finite element modeling method based on the multi-physical field finite element analysis platform, ANSYS software.A material parameter inverse seeking method based on the micro-indentation test was presented in this paper to get the material parameters of magnetic pulse bulging tube. The method combines the micro-indentation test, the validation of the finite model of micro-indentation test and the inverse seeking process based on the multiisland genetic algorithm(MIGA). The first axial crushing finite element modeling method is based on the inverse technique for determining the material constitutive parameters of magnetic pulse bulging tube. It is need to partition cross section of magnetic pulse bulging tubes into eleven component and perform micro indentation test in each component. The load-depth curve of each component can be obtained though the micro-indentation test and the load-depth curve obtained by the simulation can approach the micro-indentation test curves step by step by changing the material parameters in the finite element model. The material parameters in the finite model are considered to be the real material parameters of the magnetic pulse bulging tube, when the two curves achieve the minimum error in the least-squares sense. Finally, the material parameter in different position of the magnetic pulse bulging tube were employed into the axial crushing simulation and compare the force-displacement curve, the mean force and energy absorption obtained from simulation with the ones from test.Electromagnetic-structure coupling finite element modeling method was carried out with particular attention to the transfer of forming history from the magnetic pluse bulging simulation to the crash models. The values of tube thickness, work hardenning, and residual stresses at the end of the magnetic pluse bulging simulation were used as the initial state for the caash models. By comparing the simulation results with the axial crushing test, the reliability of the axial crushing finite element model was validated. The results showed the axial crushing finite element model could give reasonable prediction of crushing features of magnetic pluse bulging tubes. Furthermore, the axial crushing finite element model was used to explore the energy absorption characteristics of magnetic pulse bulging tubes with binding mould. The two cases of rectangular cross section mould and circular cross section mould were mainly considered.