Influence of the shape of necking area on the necking of viscous medium by outer pressure

The paper focuses on analyzing the influence of the parameters of necking area on the necking of viscous medium with outer pressure.The parameters include diameter of the tube-blank,length of the necking area and the length-to-diameter ratio (ratio of necking length to the diameter of tubular blank).Finite element methods,theoretical analysis and experiments are adopted respectively,by which the variation rules of the surface area of the tubular blank under different shapes of necking area and the influence of latter on necking deformation manners are obtained.The results show that,there is a critical necking point at the range of the length-to-diameter ratios from 0 to 0.71,where the variation of the surface area of the tubular blank turns from decreasing to increasing.As a result the deformation mode would turn from compression to tension which is beneficial for increasing the necking limit.