Research On The Theory Of Inverse Bulge Pre-deformation Of Magnetic Medium For AA5052 Sheet And Deep Drawing Process

With the improvement of the forming requirements for thin-walled and deepcavity components,the processing of sheet metal parts has gradually broken the fixed and unitary method and is no longer limited to directly forming by optimizing external conditions,rather according to the shape and process characteristics of the parts,using the soft medium to form or increase the effective pre-deformation process.The pre-deformation amount and the selection of the medium are crucial to the forming effect.Magnetorheological fluid intelligent magnetic fluid material has all kinds of outstanding advantages of soft medium forming advantages.Therefore,this paper proposes research on the deep drawing process of magnetorheological fluid sheets based on inverse bulge pre-deformation.Firstly,a theoretical model of forming pressure transfer characteristics of magnetorheological fluid was constructed independently.The results show that the pressure decreases nonlinearly with the increase of the pressure transfer distance under the condition of certain magnetic field intensity.Furthermore,the formula of contour change and stress expression of any part of the sheet during deformation are given.Secondly,the influence rule of inverse bulge pre-deformation on the deep drawing process is clarified.The deformation degree of pre-deformed parts increases with the increase of inverse bulge height.Under the same inverse bulge height,the changing trend of stress and strain states of different diameters of sheet metal is the same,and the values of large diameters are larger.Comparing the contour size of the pre-deformed parts obtained by theoretical analysis and finite element numerical simulation with the experimental results,the error is small within a certain radial distance,which proves the reliability of the theoretical calculation and the finite element model.Finally,the influence mechanism of the inverse bulge and pre-deformation on the deep drawing process of cylindrical parts is systematically described.The results show that the inverse bulge pre-deformation effectively changes the stress state of the sheet metal in the early stage of cylindrical deep drawing.With the increase of the inverse bulge height,the circumferential compressive stress at the round corner of the die increases,the stress neutral layer moves along the thickness direction,and the area of radial tensile stress expands,which is more conducive to the flow of the sheet metal.At the same time,the deformation becomes more uniform as the equivalent strain difference decreases.For the cylindrical parts with drawing ratios of 2.125 and2.25,when the height of inverse bulge pre-deformation is 9 mm and 5 mm respectively,the wall thickness variance of the cylindrical parts is the smallest,and the maximum wall thickness thinning rate is reduced to 6% and 4.4%.The above research shows that the magnetorheological fluid soft die medium sheet drawing process based on inverse bulge pre-deformation plays a positive role in improving the quality of forming parts.With the continuous improvement and improvement of the current production technology,the research on magnetorheological fluid in the field of sheet metal will be gradually deepened.