Study On Composite Forming Process Of Granular Medium For Intermediate Shield

Solid granule medium forming(SGMF)is a new soft die forming technology based on traditional soft die forming,which uses solid granule as force transfer medium instead of rigid die.The process gives full play to the characteristics of granular medium,and provides a new idea for the stamping forming of sheet metal parts with complex cross-section.As the key part of vacuum interrupter to ensure the internal components are not polluted,a composite drawing process of granular medium is proposed in this paper to solve the problem that the geometric structure of the part has complex cross-section characteristics and is difficult to form.The feature of the process is to apply proper back pressure on one side of the plate to restrain the thinning of the workpiece,so as to achieve the required cross-section shape of the part.In this paper,based on the composite drawing case of the key part of the vacuum interrupter of the electric vacuum device,the forming law of the scaling part of the intermediate shield under the back pressure in the SGMF process is studied by using ABAQUS finite element analysis and field test.Firstly,based on the ABAQUS finite element theory analysis,taking the middle shield zoom part as the research object,combined with the TU1 oxygen free copper material performance test,the ABAQUS finite element simulation model is established to explore the influence of different process paths on the forming quality of parts,and the effectiveness and feasibility of composite drawing in SGMF process are obtained.Secondly,study the change of sheet thickness,load force,contact stress,equivalent stress during the forming process,and study the influence of the change parameters of solid particle size,charging volume and back pressure on the final shape and thickness of the part.Studies have shown that the application of back pressure has a more obvious effect on the deep drawing.It is obtained:the back pressure is too large,the sheet is wrapped tighter,and the pressure of the sheet along the straight wall of the lower punch increases accordingly.At the same time,the lower punch The radial tensile stress on the plate at the punch fillet position is also increasing,which intensifies the thinning of the plate,which will seriously cause cracks;if the back pressure is too small,the central part of the plate will be rapidly thinned,which will occur in the subsequent stage of descent.The phenomenon of sidewall wrinkles and stacking;reasonable back pressure can effectively suppress sheet metal thinning.Finally,through the forming test of the TU1 oxygen-free copper intermediate shielding cover scaled-down pieces,the effect of the back pressure during the forming process was verified,and the intermediate shielding cover Scaled-down pieces was successfully trial-produced by taking the blank with the initial diameter D₀=80mm.