The Yield Behavior Research And Finite Element Simulation Of QP Steel

Flexible roll-die forming is a new kind of plastic forming technology which accord with the concept of energy-saving and lightweight development.But in the forming experiments with dual-phase steel,the variable cross-section bottom area have emerged some defects such as hump-up and edge wave because of residual stress,which influenced the forming accuracy.This topic is aimed at engineering problems for building components of flexible roll-die forming machine to reduce the forming force,promote accuracy and optimize process equipment.The mechanical properties,yield behavior and simulation of Quenching and Partitioning steel are studied in order to find a new high strength steel which is suitable for flexible roll forming.This article is based on research goals.First,30 times of tensile experiments were designed for QP980 materials.The basic mechanical properties and true stress-strain relations of QP980 were obtained according to uniaxial tensile experiments with different rolling direction,and true stress-strain relations under biaxial tensile experiments with different biaxial loading paths were obtained.According to the above data,the plastic work contour picture is drawn based on the principle of plastic work equivalent.Then the paper explores the deformation behavior of QP980 steel.Six kinds of yield criterions such as Mises,Hill'48,Hill'93,Hosford,Gotoh and Barlat89 were analyzed and verified to find a most suitable yield criterion to describe the deformation behavior of QP980.And the results show that Hill'48 is the most suitable yield criterion for QP980.In addition,Hill '48 yield criterion was optimized in order to better describe the yield behavior of QP980.Finally,a finite element analysis based on the previous conclusions was carried out to forecast the forming effect.The forming result of finite element simulation went well and did not cause defects such as hump-up and edge wave.The equivalent stress,equivalent plastic strain,roll forming force and torque,springback of plate were obtained at the same time,except that the springback angle is a little big,others fully met the design requirements of variable height flexible roll-die forming machine.Those analyses show that QP980 is feasible in roll forming on this flexible roll-die forming machine.