Research On The Influence Of The Coupling Effect Between Variable Gap And Variable Blank Holder Force On The Deep Drawing Earing

Deep drawing is a plastic processing method of punching an effigurate blank into an uncork hollow part with the effect of a die.Due to its anisotropic properties during the drawing process,the blank will have an uneven earing phenomenon of the cylinder wall.The production of the earing is not only reduced the utilization of the material,but also increased the trimming process,and in severe cases,the workpiece will be badly broken during the subsequent drawing.There are two main factors affecting earing production:one is a directional factor;the other is a non-directional factor.The directional factors mainly include the yield ratio and texture coefficient of the sheet,while the non-directional factors refer to the blank holder force,the die gap,the radius of the round corner of concave-convex die,and the shape of the blank.Although these two factors will lead to the earing phenomenon,their effects on the earing are independent with each other.Reasonable adjustment of these two factors restricts each other,in this way the sheet can be uniformly deformed during the drawing process,thereby achieving a reduction of earing rate.Therefore,with the purpose of study of the coupling effect between variable gap and variable blank holder force on the deep drawing earing,this subject used finite element(FEM,Finite Element Method)to carry out simulation analysis to study the effect of BHF(Blank Holder Force)on the earing of deep drawing part during the deep drawing with variable gap.The best variable blank holder force loading curve during the variable gap drawing was discussed,so as to reduce the earing rate of the sheet material deep drawing and improve the forming quality of the deep drawing workpiece.In this paper,the constitutive equation describing the deformation of elastoplastic body is established based on the Hill48 anisotropic yield criterion.Then the influence mechanism of the variable gap drawing on the sheet material in different directions of the cylindrical part is analyzed.The theoretical model of the cylinder wall's height is established,and then using the quasi-static method of Abaqus/Explicit,the finite elementsimulation model is established for the variable gap drawing of the cylindrical part.The finite element simulation of the 0.8mm thick DC04 steel plate with variable gap under different numerical blank holder force conditions and four classical variable blank holder force loading schemes is carried out.The simulation results show that the blank holder force has a great influence on the cylindrical parts to change the variable gap deep drawing earing.There is a big difference in the rate of deep earing under the different blank holder force loading scheme.As for the variable gap drawing with the constant blanking holder force,the fitting analysis by MATLAB software found that under the condition of the same variable gap value,when the blanking force is small,the rate of the variable gap drawing earing is higher.Increasing the blank holder force within the range can effectively improve the effect of reducing the earing rate;when the blank holder force exceeds a certain range,the influence of the blank holder force on the variable gap deep drawing earing tends to be gentle.Compared with the variable gap drawing under the constant blank holder force loading scheme,the variable blank holder force loading scheme has different effects on the variable gap deep drawing earing,and the “?” type and the decreasing type blank holder force are more favorable.But the“V” type and the increasing type of blank holder force are not conducive to the reduction of the reduction of the variable gap deep drawing earing.It can be seen from the situation that the variable gap deep drawing ear under various blank holder force loading schemes can only make full use of the coupling effect of the variable gap and the variable pressure side force to fully exert the forming property of the sheet material,thereby obtaining more than simple use,which achieves the purpose of producing low earing or even no earing deep drawing parts.In this paper,the simulation results are also verified.Through the variable gap drawing test of cylindrical parts under different blank holder force conditions,it is proved that the reasonable variable blank holder force loading method can effectively match the variable gap drawing to reduce the earing rate.At the same time,if the unreasonable variable blank holder force loading method is used will hinder the variable gap drawing to reduce the rate of drawing earing,and the earing phenomenonwill be aggravated.The test results consistent with the simulation results show the accuracy of the finite element analysis,indicating that the finite element method is suitable for numerical simulation of variable gap drawing,which can be used to determine a reasonable blank holder force loading scheme.