Hyperplastic Forming: Process Potential and Factors Affecting Formability

Abstract

This paper has two distinct goals. First, we argue in an extended introduction that high velocity forming, as can be implemented through electromagnetic forming, is a technology that should be developed. As a process used in conjunction with traditional stamping, it may offer dramatically improved formability, reduced wrinkling and active control of springback among other advantages. In the body of the paper we describe the important factors that lead to improved formability at high velocity. In particular, high sample velocity can inhibit neck growth. There is a sample size dependence where larger samples have better ductility than those of smaller dimensions. These aspects are at least partially described by the recent model of Freund and Shenoy. In addition to this, boundary conditions imposed by sample launch and die impact can have important effects on formability.

Formability of steel sheet in high velocity impact

“…The results clearly show that the useful formability of the low-ductility steels can be dramatically improved by this mode of forming, but it is far less effective at increasing the ductility of the materials that already have good quasi-static formability. This can be rationalized by published ideas about improvements in instability strain due to high velocity deformation [11,12] and through-thickness compressive stress due to impact [10]. In high velocity deformation the sheet's mechanical boundary conditions may be more important than the material's quasistatic ductility in determining its high velocity formability.…”

“…A general and comprehensive understanding of high velocity formability is not presently available. However some important qualitative concepts are now clear [6,10]. First, it appears that rather than strain-rate induced changes in constitutive behavior, inertial effects are primarily responsible for the increased ductility at high forming velocities.…”

Characterization of Gallium-induced Intergranular Fracture Surface and the Auger Electron Spectroscopic Analysis for Mg Grain Boundary Segregation in AA6061 T4 Al-Mg-Si Alloy

“…AA6xxx Al-Mg-Si alloy is such an alloy because 6xxx series alloy can be hardened during baking. 1,2) However, since available 6xxx series alloys are more difficult to form than 5xxx series alloys, 3,4) so a better forming technique or a new 6xxx alloy, which combines high formability and bake hardness needs to be developed. 1) Deformation at warm or high temperature is a promising approach to improving the formability of 6xxx series alloys.…”

Effects of current frequency on electromagnetic tube compression

“…The distribution and amplitude of the magnetic pulse pressure can be controlled by the spatial configuration of actuators (often a solenoid coil) and the stored charge in capacitor bank. So the electromagnetic forming process is flexible and easy to apply and control (Daehn et al, 2000;Resch et al, 2004). The electromagnetic forming technology has peculiar advantages in forming, joining and assembly of the lightweight metal materials, such as aluminum, because of improved formability, improved strain and the workpiece.…”