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Title: Evaluation of Forming Limit by the 3 Dimensional Local Bifurcation Theory

Abstract

A theoretical prediction and evaluation method for the sheet metal formability is developed on the basis of the three-dimensional local bifurcation theory previously proposed by authors. The forming limit diagram represented on the plane defined by the ratio of stress component to work-hardening rate is perfectly independent of plastic strain history. The upper and the lower limit of the sheet formability are indicated by the 3D critical line and the Stoeren-Rice's critical line on this plane, respectively. In order to verify the above mentioned behavior of the proposed forming limit diagram, the experimental research is also conducted. From the standpoint of the mechanical instability theory, a new concept called instability factor is introduced. It represents a degree of acceleration by current stress for developing the local bifurcation mode toward a fracture. The instability factor provides a method to evaluate a forming allowance which is useful to appropriate identification for a forming limit and to optimize the forming condition. The proposed criterion provides not only the moment to initiate the necking but also the local bifurcation mode vector and the direction of necking line.

Authors:
;  [1]; ; ;  [2]
  1. SUMITOMO METAL INDUSTRIES, LTD. 1-8 Fuso-cho, Amagasaki Hyogo 660-0891 (Japan)
  2. M and M Research, Inc., 4-15-3 Jingumae, Shibuya-ku, Tokyo 150-0001 (Japan)
Publication Date:
OSTI Identifier:
21057366
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 908; Journal Issue: 1; Conference: NUMIFORM '07: 9. international conference on numerical methods in industrial forming processes, Porto (Portugal), 17-21 Jun 2007; Other Information: DOI: 10.1063/1.2741010; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ALLOYS; BIFURCATION; FRACTURES; INSTABILITY; MATERIALS WORKING; METALS; SHEETS; STRAIN HARDENING; STRAINS; STRESSES; THREE-DIMENSIONAL CALCULATIONS

Citation Formats

Nishimura, Ryuichi, Nakazawa, Yoshiaki, Ito, Koichi, Uemura, Gen, and Mori, Naomichi. Evaluation of Forming Limit by the 3 Dimensional Local Bifurcation Theory. United States: N. p., 2007. Web. doi:10.1063/1.2741010.
Nishimura, Ryuichi, Nakazawa, Yoshiaki, Ito, Koichi, Uemura, Gen, & Mori, Naomichi. Evaluation of Forming Limit by the 3 Dimensional Local Bifurcation Theory. United States. doi:10.1063/1.2741010.
Nishimura, Ryuichi, Nakazawa, Yoshiaki, Ito, Koichi, Uemura, Gen, and Mori, Naomichi. Thu . "Evaluation of Forming Limit by the 3 Dimensional Local Bifurcation Theory". United States. doi:10.1063/1.2741010.
@article{osti_21057366,
title = {Evaluation of Forming Limit by the 3 Dimensional Local Bifurcation Theory},
author = {Nishimura, Ryuichi and Nakazawa, Yoshiaki and Ito, Koichi and Uemura, Gen and Mori, Naomichi},
abstractNote = {A theoretical prediction and evaluation method for the sheet metal formability is developed on the basis of the three-dimensional local bifurcation theory previously proposed by authors. The forming limit diagram represented on the plane defined by the ratio of stress component to work-hardening rate is perfectly independent of plastic strain history. The upper and the lower limit of the sheet formability are indicated by the 3D critical line and the Stoeren-Rice's critical line on this plane, respectively. In order to verify the above mentioned behavior of the proposed forming limit diagram, the experimental research is also conducted. From the standpoint of the mechanical instability theory, a new concept called instability factor is introduced. It represents a degree of acceleration by current stress for developing the local bifurcation mode toward a fracture. The instability factor provides a method to evaluate a forming allowance which is useful to appropriate identification for a forming limit and to optimize the forming condition. The proposed criterion provides not only the moment to initiate the necking but also the local bifurcation mode vector and the direction of necking line.},
doi = {10.1063/1.2741010},
journal = {AIP Conference Proceedings},
number = 1,
volume = 908,
place = {United States},
year = {Thu May 17 00:00:00 EDT 2007},
month = {Thu May 17 00:00:00 EDT 2007}
}