The formability of steel sheets must be improved to form complicated car parts. Multistep forming is one way of improving the formability. The shape after preforming could influence the formability in the main step of multistep forming. However, no relationship has been reported between the shape after preforming and the final shape in the case of stretch forming. In this study, circular truncated cones were formed by two-step forming consisting of preforming and main forming, with combinations of various shapes after preforming and final shapes in order to investigate the effect of the shape after preforming on the forming limit in final forming. The results show that the forming limit height in main forming is affected by the preforming shape. In addition, the forming limit height in main forming is determined by the central cross sectional line length of the shape after preforming.

In this study, punchless punching by the compression ignition of octane and the effect of varying the amount of fuel on punchability were investigated. In the experiment, the compression in compression ignition was applied using a drop hammer. As the amount of fuel increased, the variation in the initial height of the hammer required for completing the piercing could be divided into the following four parts o the basis of the amount of fuel. In the first part, corresponding to the smallest amount of fuel, the height exhibited a large decrease. In the second part, the height decreased by a small amount. In the third part, the height increased. Finally, in the fourth part, corresponding to the largest amount of fuel, the height remained constant. The four parts were believed to be caused by differences in the chemical reactions. Moreover, the optimum amount of fuel for punching was the largest amount of fuel under the conditions of the first part.

Flame-resistant magnesium alloy containing Ca is attracting attention in the transportation field because it is safe and lightweight. In this study, the effects of texture on bending formability were investigated for samples having different forms of texture that were cut from an extruded Mg-Al-Zn-Ca alloy plate at different angles ranging from 0° to 90° from the extrusion direction. Tensile and compressive deformation behaviors were also examined to discuss the shift of a neutral layer in bending. For bending, it was shown to be preferable that the basal texture not be inclined in low-strain region because of tension/compression asymmetry. However, in high-strain region, the influence of the shift of the neutral layer was weakened. In the experiment, the sample with a cutting angle of 45° exhibited the best bending formability. Furthermore, the result of a verification test using a sheet fabricated by a lateral extrusion, named friction-assisted extrusion (FAE), in which the basal texture was controlled to be inclined, showed that FAE improves the bending formability. This was confirmed by microstructural observation of the cross section near the tension surface at the same bending radius. The number of deformation twins that cause voids and cracks was reduced by controlling the basal texture to be inclined.