Abstract
Drawability of metal sheets is indicated by Swift’s L. D. R., C. C. V. of Fukui’s test, and the plastic strain ratio r. Swift’s L. D. R. and C. C. V. of Fukui’s test are based on the deep drawing test, while the plastic strain ratio r is determined simply by the tensile test. It has been reported by many investigators that these values are excellent indicators of drawability. But it is difficult in practice to indicate the drawability of thin sheets by Fukui’s test and the plastic strain ratio r. On the other hand, Swift’s test is favorable for thin sheets, but in addition to the complexity to determine the L. D. R. of metal sheets, the reproducibility of the value obtained is doubtful.
So in this paper the validity of the load deep drawing method was discussed, where the value is indicated by the ratio of fracture load in the cup wall to the maximum load to deform the flange. Although the fracture load must be kept constant irrespective of the drawing ratio, the observed values are at variance, and therefore L. D. R. of metal sheets cannot be determined by this so-called T. Z. P. method. But it has been found that the fracture loads of the cup wall in various drawing ratios can be kept constant by a suitable lubricating operation, thus enabling the load deep drawing method to determine the drawability of thin metal sheets.
