Study On New Process Of Back Pressure Deep Drawing With Using Solid Granule Medium Forming Technology In Cylindrial Parts

Solid Granule Medium Forming Technology(SGMF process)is a soft mold forming process that has developed rapidly in recent years.It is widely favored due to its simple mold and good forming effect.However,the bottom portion of the process forming deep drawing specimen is subjected to the biaxial tensile stress state and the thinning is more serious,which limits its application in a production project requiring high wall thickness.The back pressure drawing process is a process scheme proposed to reduce the wall thickness reduction of the bottom portion of the drawing member.The pressure is mainly applied to the bottom of the sheet by the back pressure punch to increase the friction of the bottom metal flow.The effect of suppressing the thickness reduction of the bottom wall is suppressed.In this paper,the research on the back pressure drawing process of cylindrical solid particle media is carried out.The mechanical model of the back pressure deep drawing of the cylindrical solid particle medium was established by theoretical method.The stress state of the flange zone,the straight wall zone,the convex die fillet zone and the bottom zone of the cylinder was studied.And a equation about the unit pressure of the punch during the drawing process was derived.The forming process of SGMF back pressure drawing process was studied by numerical simulation and experiment.The influences of back pressure,initial position of back pressure punch,roughness of back pressure punch and shape of back pressure punch on the wall thickness distribution of sheet were studied.The results show that the greater the back pressure,the closer the initial position of the back pressure punch to the sheet material,or the rougher of the back pressure punch,the more the thickness reduction of the bottom wall can be suppressed.The convex back pressure punch can effectively suppress the wall thickness reduction in the center of the cylinder bottom,and the concave back pressure punch can effectively The wall thickness of the outer edge and the rounded area of the bottom portion of the cylinder is suppressed from being reduced.The back pressure drawing experimental mold was designed,and the effects of back pressure,initial position of the back pressure punch,shape of the back pressure punch on the ultimate drawing ratio and the maximum pressure of the punch required for forming were investigated experimentally.The results show that the suitable back pressure parameters can effectively increase the ultimate drawing ratio of the sheet.When the back pressure spring stiffness is 82N/mm,the back pressure punch initial position and the sheet distance are 10 mm,the draw ratio is 2.08.The workpiece;the greater the back pressure,the closer the initial position of the back pressure punch is to the sheet material,the greater the punch pressure required for deep drawing;the maximum punch pressure required for deep drawing with the convex back pressure punch,using the concave back pressure punch Deep punch pressure is minimal.