Finite Element Analysis Of DP780 High Strength Steel Sheets Electromagnetic Forming

Electromagnetic forming,because of its advantage of improving the formability of materials,which makes it possible to solve the forming problem of high strength steel.In this paper,the high speed constitutive model and dynamic deformation behavior of DP780 high-strength steel was studied,and the finite element simulation and process parameters of plate electromagnetic forming based on driving diaphragm also been investigated,which provided the theoretical basis for the research of electromagnetic forming of high strength steel.The stress-strain curves of specimens under different strain rates were obtained by quasi-static tensile experiment and the dynamic tensile test of the split Hopkinson bar,the influence of strain rate on the mechanical properties of DP780 was analyzed,and the Johnson-Cook constitutive model of high strength steel under the condition of higher strain rate was established.The results show that: the yield strength and ultimate tensile strength of the specimen increase significantly when the strain rate rose from 1150s-1 to1900s-1,and the DP780 has a certain strain rate sensitivity;when the strain rate continued to rise to 2800s-1 and 4200s-1,the changes were not obvious,and even the ultimate tensile strength decreased slightly,which was due to the effect of thermal softening effect on the material mechanical properties resulting from adiabatic temperature rise.Based on the finite element software-Ansys,a circuit and a two-dimensional magnetic field model were established in the Multiphysics module,and the results were obtained through the analysis,such as discharge currents,current of the driving plate,distribution of the magnetic field model and the field force on the driving plate.In order to realize the finite element simulation of the electromagnetic forming process of high strength steel slab,the structure field was analyzed by ANSYS/ LS-DYNA explicit analysis module,the transmission of magnetic force load was compiled by using APDL orders,and the parameters of J-C constitutive model were extracted.Combined with the orthogonal test,the influence of the discharge voltage,discharge frequency,the thickness of the driving plate and the distance between the driving plate and the coil were studied.The results show that: the higher the discharge voltage,the larger the discharge energy and the higher the bulging height of the slab;thedischarge frequency has the most significant influence on the bulging height,and the driving film thickness has the least influence.With certain limits,the smaller the distance between the driving plate and the coil could be better,and considering the practical application,the gap value should be about 2mm.