Masaru Kobayashi

A study of springback in the stretch bending of channels

Abstract The main problems associated with the bending of channels are springback, undesirable deformation of the sectional shape and buckling of the flanges; it is said1that the stretch bending method is effective in overcoming these problems. Regarding the springback, it is important in an actual process to know not only the amount of springback but also the variation of springback with the mechanical properties of the material of the channel and with its dimension. Especially, when SUS304 stainless steel is used for the channel material, the variation of mechanical properties is unavoidable and will depend upon the environmental temperature, the forming speed, the chemical composition and the working history. In this paper, springback in the stretch bending of channels has been studied theoretically and experimentally, and the relationship between the mechanical properties and springback has been clarified. The calculated values of springback are in good agreement with the measured values. Springback decreases with increasing tension, and an additional tension is more effective than an initial tension. It is confirmed that the variation of springback due to the variation of the mechanical properties and dimensions of channels is reduced by using the “fixed initial elongation method”, in which the initial elongation caused by the initial tension is kept constant.

Press Formability of Face-Centred Cubic Metals at Cryogenic Temperatures

The increase in the ductility of F.C.C. metals at cryogenic temperatures is due to the strain propagation facilitated by the increase in the work-hardening rate. In order to apply these characteristics to practical forming processes, the influence of cryogenic temperatures on the formability of copper and aluminium sheets in stretching, deep drawing and hole flanging was studied.