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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

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Title: 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
Other Titles: 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
Authors: 横井, 龍雄1 Browse this author
首藤, 洋志2 Browse this author
池田, 賢一3 Browse this author →KAKEN DB
中田, 伸生4 Browse this author
土山, 聡宏5 Browse this author
大村, 孝仁6 Browse this author
峯, 洋二7 Browse this author
高島, 和希8 Browse this author
Authors(alt): Yokoi, Tatsuo1
Shuto, Hiroshi2
Ikeda, Ken-ichi3
Nakada, Nobuo4
Tsuchiyama, Toshihiro5
Ohmura, Takahito6
Mine, Yoji7
Takashima, Kazuki8
Keywords: dual-phase steel
hole expansion test
electron backscatter diffraction
nano indentation
local strain mapping
strain distribution
micromechanical characterization
strain localization
grain refinement
shear fracture
Issue Date: May-2016
Publisher: 日本鉄鋼協会
Journal Title: 鉄と鋼
Volume: 102
Issue: 5
Start Page: 244
End Page: 252
Publisher DOI: 10.2355/tetsutohagane.TETSU-2015-087
Abstract: Dual Phase (DP) steel is used in automotive body parts for weight saving and crashworthiness, however there is an issue of DP steel in low stretch flange ability evaluated by hole expanding tests. In order to improve stretch flange ability of DP steel, it is important to estimate the damage of punching quantitatively and to clarify the change of microstructure before and after punching because the hole expansion ratio is decided in the ductility remained after pre-strain equivalent to punching. Therefore we tried to measure the damage of punching by unique techniques of Electron Backscatter Diffraction (EBSD), nano-indentation and micro-tensile testing and to observe fracture surface by Scanning Transmission Electron Microscope (STEM). Average EBSD-Kernel Average Misorientation (KAM) value and pre-strain damage have strong correlation, thus average KAM value can become the index of the damage. The nanohardness and tensile strength using micrometer-sized specimens increased with increasing average KAM value in the ferritic phase as approaching the punching edge. A shear type fracture occurred without necking in the specimen cut out in the area of the edge. The ultrafine-grained ferritic microstructure was observed in the sample cut out in the same area with STEM. It seems that the ductility loss of the punched DP steel was probably attributed to localized strain into the ultrafine-grained ferritic microstructure.
Rights: 著作権は日本鉄鋼協会にある
Type: article
Appears in Collections:工学院・工学研究院 (Graduate School of Engineering / Faculty of Engineering) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 池田 賢一

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