Numerical Simulation And Experimental Research On The Forming Process Of A H70 Shell Body

A new type of shell body has the structural characteristics of thin wall and thick bottom.If the spinning forming process is used,the side wall is prone to instability and depression under the pressure of the spinning wheel,and the process is complex,inefficient,and costly,making it unsuitable for mass production.On the basis of analyzing its structural characteristics,in order to improve tissue density and mechanical properties,it is advisable to use precision forming methods to produce such parts.This article proposes a production process that mainly relies on plastic forming at room temperature and supplemented by machining.Through simulation and experimental research,the new forming process for the shell body has been determined as follows: blank punching cup four times thinning and drawing taper shaping four times closing forming machining.Analyzing the structural characteristics of the product,the shell body exhibits uniform changes in taper and varying wall thicknesses.After multiple simulations and experimental results,it has been found that during the closure deformation of the cartridge case,the changes in wall thickness of the three parts,namely the force transfer zone to be deformed,the inclined shoulder deformation zone,and the deformation completion zone,are different.Among them,the wall thickness difference in the deformation zone of the inclined shoulder is the largest,the wall thickness near the transmission zone is the thinnest,and the wall thickness near the deformation completion zone is the thickest;The wall thickness of the force transfer zone to be deformed remains basically unchanged;The wall thickness increase in the deformation completion zone is the largest,but the wall thickness difference is very small.Based on the characteristics of product structure and wall thickness changes,this article accurately designs a drawing punch with gradient diameter changes in the thinning drawing process,which can obtain drawing parts with different wall thicknesses in different regions to ensure that the extruded parts meet the dimensional accuracy requirements of the product and improve the forming quality.During the closure forming process,the new type of shell body is calculated according to the traditional closure theory.The force transmission area and inclined shoulder deformation area of the shell blank are both subject to forming instability problems,and the wall thickness of the workpiece mouth is severely thickened,exceeding the product size requirements.Through DEFORM simulation and experimental research,this article obtains the deformation conditions for the deformation zone and force transfer zone of the blank that do not experience instability and have the simplest process;For the wall thickness of the shell opening,the traditional closing forming process of this shell can be modified by increasing the closing coefficient and using a four time closing process to control the increase in wall thickness of the opening,and making the product meet the product size requirements.Through mechanical tensile tests,it was found that the tensile strength and elongation of the shell casing parts meet the product performance requirements.Verified the theoretical defects of traditional necking forming theory for special materials,determined the forming process of a new type of shell body,and provided a theoretical basis for the forming of similar thin-walled shell parts.