Research On Carbon Black-Modified Magnetorheological Elastomer Assisted Deep Drawing Process

Deep drawing is an important branch of plastic forming,which has the characteristics of high production efficiency,material saving and excellent strength and stiffness of formed products,so it is widely used in various fields such as aerospace,automobile,ship and civil products.However,because the forming quality of parts is limited by the fluidity of the blank and the interaction between the die and the blank during the drawing process,the wrinkling and cracking of the workpiece often occur during the drawing process.In order to improve the success rate of deep drawing,parts with larger depths often require multiple deep drawings to form,which also makes deep drawing forming of deep parts challenging.Flexible-die forming is a fast developing forming method.Compared with the traditional rigid die,the flexible die will reduce the concentrated stress of the sheet during the drawing process and reduce the probability of "dangerous section".Magnetorheological Elastomers(MRE)is a new type of intelligent material.Its mechanical properties can change with the change of magnetic field strength,which makes MRE have a wide application prospect in many fields.To solve the problems in traditional deep drawing processes.In this paper,MRE is selected as the drawing flexible-die,which can not only improve the forming quality of the drawing parts,but also realize the intelligent control of the drawing process through the change of the external magnetic field.In addition,reinforcement was carried out on MRE to improve its mechanical properties.The main contents of this paper are as follows:(1)In this paper,four kinds of MRE were prepared using natural rubber as matrix,carbon black and carbonyl iron powder.Its microstructure was observed by field emission scanning electron microscope(SEM),and its mechanical properties and magnetorheological(MR)effect in shear were observed and analyzed by electronic universal testing machine and advanced rotary rheometer.The experimental results show that the addition of carbon black improves the tensile strength and 300%constant tensile force of MRE.What is more noticeable is that carbon black changes the Mullins effect of MRE under low strain,and the MR effect of MRE with 30%iron powder volume fraction added with carbon black is significantly improved.This proves that using carbon black as reinforcing agent can greatly improve the properties of MRE.According to the national standard GB/T 7757-2009,the compression test samples of each group of MRE were prepared and the MRE compression test platform was built.The self-made platform can apply 0-300mT variable magnetic field during the sample compression process.The mechanical behavior of each group of samples under different magnetic fields was tested using a self-made compression platform,and the MR effect of each group of samples under compression was obtained.Comparing the MR effect of MRE in compression and shear,it is found that MRE has stronger MR effect in compression.Through the analysis and discussion of the test results,the formula of MRE used in the deep drawing process was finally determined.The MRE prepared by this formula has good mechanical properties and MR effect,which can meet the requirements of the drawing process for die materials.(2)The finite element analysis platform ABAQUS is used to simulate the deep drawing process.The hyperelastic mechanical model is discussed and analyzed,and the mechanical model of the MRE sample prepared in this paper is determined.The Mooney-Rlivlin model parameters of MRE are obtained using the material evaluation module.The material parameters are applied to the numerical simulation,and the reasonable model structure,mesh size and boundary conditions are combined to make the numerical simulation better match the actual working conditions.The influence of MRE flexible-die and traditional rigid die on sheet metal deep drawing is compared by simulation results.It is found that the use of MRE flexible-die can reduce the stress on the sheet,reduce the thinning rate and springback amount,and effectively improve the success rate of deep drawing parts.In addition,by changing the magnetic field,the forming result can be effectively controlled and changed,and the intelligent control of the deep drawing process can be realized.Finally,based on the simulation results,this paper designs the magnetorheological assisted drawing device.And conduct engineering experiments to prepare qualified parts.