Investigation of the Drawability of Sheet Metals (Measurements of r Values of Sheet Steel)

For assessing the qualities of sheet metal for deep-drawing by the tension test, γ value is adopted generally. However, it is difficult and complicated to obtain the precise value of it. In order to obtain the value precisely and easily, the authors have made trialy the devices to measure directly the elongation and the reductions of width and thickness; these devices are transducers to which the electrical resistance strain gauges are applied. By using these devices, precise, continuous, multipoint and quick measurement can be done. It has been clarified by the continuous measurements that γ values are not the same relating to the elongations. It is recommended that one uses γ value obtained at about 25% elongation.