Study On Effect Of Plastic Strain Ratio On Sheet Metal Drawing Deformation

Sheet metals have the characteristics of high production technological level and high added value,which are important raw materials for industrial production.With the improvement of industrial level,the demand for sheet metals will gradually increase.Therefore,the development of new steel grades with better performance and performance optimization and lowering cost of existing steel grades has always been a primary task for steel practitioners.Plastic strain ratio is the main parameter reflecting the formability of sheet metal,which controls the deformation in different directions in the sheet metal forming.The deformation of sheet metal during deep drawing is complicated,and the stress and strain states of the flange,fillet and straight wall regions are different.In this paper,the effect of plastic strain ratio in the different deformation zones of drawing parts during the deep drawing process has been taken as the research purpose,and its influence on deep drawing and cracking is emphatically analyzed.Firstly,the stress strain of the cylindrical part drawing process has been analyzed and the calculation formula of the drawing force has been derived.Through the formula,the influencing factors of drawing force and the stress state of the risk area have been analyzed.Secondly,numerical simulation software Dynaform was used to simulate deep drawing under different r-value settings,and the stress and strain conditions in the flanges and risk area as the main deformation zone of the cylinder have been analyzed.Finally,to verify the reliability of simulation results,the DC series deep drawing sheet metal were used for the actual deep drawing experiments.According to the results of drawing force formula,numerical simulation and actual drawing experiments,it is considered that the forming performance of the sheet metal is mainly improved by the plastic strain ratio reducing the deformation stress of flange and the thinning of the risk area.For numerical simulation,the actual anisotropic material model has been found to increase the drawing force and decrease the thinning of the risk area of smaller plastic strain ratio direction.However,it has less effect on isotropic material model.Meanwhile,the performance is weaker in the direction of comparatively small plastic strain ratio and more easily to crack.In practical production,the average value of plastic strain ratio in three directional is used,as a parameter index to measure the anisotropy of the sheet metal will not fully indicate the performance of the material,especially when the strain variables in different directions are different.The differences of the material performance in different direction are clearly confirmed is favorable to making full use of material properties.