49 巻 (2008) 573 号 p. 0985-0989
A locally thick blank was employed for the stamping of thin high strength steel sheets to increase the wall thickness at the inner corner of stamped products. To form the locally thick blank, a 2-stage local thickening process was developed for increasing the thickness of a blank at the portion equivalent to the inner corner. In the 1st stage of the local thickening process, a ring including the portion equivalent to the inner corner is drawn, and the drawn ring is compressed with the flat tools in the 2nd stage to attain a local increase in wall thickness. The 2-stage local thickening process was designed from both finite element simulation and an experiment. A locally thick blank having an increased wall thickness of 8% was formed, and the wall thickness at the inner corner of the stamped wheel disk from the locally thick blank was successfully increased by 9.6%. It was found that the locally thick blanks are attractive for controlling the distributions of the wall thickness of stamped products from thin high strength steel sheets.