DP鋼の打抜き大変形の定量的評価とそのミクロ組織変化（第1報）DP鋼の打抜きダメージの定量化手法の提案
(Quantification of large deformation with punching in dual phase steel and change of its' microstructure - Part I: Proposal of the quantification technique of the punching damage of the dual phase steel )