Study On Forming Conditions For One-Operation Deep Drawing In Conical Part Of Thin Wall

Sheet metal forming is widely used in the manufacturing of automobile, locomotive,airplane and meters. Plastic tension instability and compression instability are two kindsof ordinary damage. To study the pattern of these two kinds of damage is the basis ofsheet metal processing and die designing. During the stretch forming of cone parts, thereare not only damage of tension instability, but also damage of compression instability.To understand the manufacturing rule and damage principle of stretch forming of coneparts can provide references for the study of the stretch forming of complicated parts andlarge coverings. Therefore, both internal and foreign scholars have paid more attentionsto the study of the stretch forming rules of cone parts. This paper presents further studiesof stretch forming of cone parts at the following points:1. By the use of analysis method, the stretch forming process of cone parts and themodeling displacement and strain of points on the cone wall are analyzed andcalculated, thus the maximum suspended displacement point can be obtained. Thering of semi-finished product having the maximum suspended displacement is callthe key ring. By the deformation analysis of the key ring, the concept of criticalrelative thickness and its calculation formula are derived. According to the criticalrelative thickness, the stretch forming can be divided into the stretching of thick wallcone parts and the stretching of thin wall cone parts. Because the thin wall cone partsis greatly different from the thick wall cone parts in the stretch manufacturing and thedie structure, this paper only presents further analysis of the stretch forming of thethin wall cone parts.2. During the stretching of thin wall cone parts, flange deformation area and cone walldeformation area are the main deformation areas. Considering the condition of thematerial stiffening during forming, and by the use of the force method, this paperbuilt up an analysis formula to calculate the loads required for the deformations offlange and cone wall of the thin wall cone parts. These studies derived mechanicalcondition required for flange deformation.3. Cracking on the small end is the ordinary failure pattern of stretch forming of the thinwall cone parts. The main reason of failure is improper control of the correct criticalload capacity for the material. In consideration of the condition of material anisotropy,analytical calculation formula of critical load capacity on the circular corner of thesmall end is built up by the instable theory of Swift dispersivity. This analyticalformula can be also the reference basis of stretch forming of the large coverings.4. On the basis of modeling analysis in the stretching process of the thin wall cone parts,the characteristics of difficulty to withstand pressed stress on the surface of the thinsheet as well as the dependence of the weft contraction upon the warp tension wereused. According to the maximum warp tension stress capably provided by thedangerous section of the small end of the thin wall cone part, the maximum weftrelative stretching height of non-compressed instability for the stretching of the thinwall cone parts was derived.5. Based on the above theoretical explanation analysis, this paper presents furtherstudies of the stretch forming of thin wall cone parts by the use of numerical analysismethod and the experimental study method. The result of the numerical analysis andthe experimental study is coincident with the result of theoretical explanationanalysis.