Research On Flexible Drawing Die And Its Key Technology Based On Magnetorheological Elastomer

Deep drawing is an important way of sheet metal forming.When the sheet metal with complex shape is obtained by using the press,the drawing stress of the existing drawing die can not be effectively controlled in the drawing process,resulting in uneven deformation of the workpiece,damage of the workpiece and high defective rate.The main reasons are as follows:1)most of the deep drawing dies use spring as buffer mechanism,without feedback system,the damping and stiffness are uncontrollable,so it is impossible to control the forming effect of the deep drawing workpiece;2)The supporting part of the stress surface of the drawing die mainly adopts the hydraulic system,which has high requirements for sealing and machining accuracy.The hydraulic system has low response sensitivity and poor stability,so it is unable to control the stress and vibration during drawing.In this paper,a flexible drawing die based on magnetorheological elastomer is designed,which uses magnetorheological elastomer with controllable damping function as buffer and vibration damping element.It can control the punching force in the drawing process under the action of external current,so that the elastic deformation of workpiece can be effectively released.It has the advantages of fast reaction speed,simple structure and high precision It has the advantages of strong controllability.In this paper,the micro force analysis of magnetorheological elastomer is carried out,and the reasons for its chain formation and normal force enhancement are obtained.Based on the dipole model and chain model,the magnetostrictive compression force and magnetostrictive compression modulus are analyzed theoretically,and the variation law is studied.The macro viscoelastic model of magnetorheological elastomer is constructed,and the constitutive equation and the calculation formula of output damping force are obtained.Different mass fraction(0%,5%,10%)of nano particles(nano-Fe₃O₄ and nano-Cu O)were added into the micro magnetorheological elastomer.The compression magnetorheological effect of the micro magnetorheological elastomer was tested by the designed test platform,and a new micro nano magnetorheological elastomer with excellent compression magnetorheological effect was obtained.A kind of magnetorheological elastomer buffer device for drawing die is designed.The internal magnetic field of the buffer device is calculated and simulated.The rationality of the magnetic circuit design is explained.A flexible drawing die based on magnetorheological elastomer is designed.The basic principle of the damping force produced by the magnetorheological elastomer buffer device and the closed-loop control principle of the stamping process are introduced,It provides a theoretical basis for the experimental study of flexible drawing die based on magnetorheological elastomer.