Vol. 1, No. 2, 2006

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ISSN: 1559-3959
Observations of anisotropy evolution and identification of plastic spin parameters by uniaxial tensile tests

Yangwook Choi, Mark E. Walter, June K. Lee and Chung-Souk Han

Vol. 1 (2006), No. 2, 301–323
Abstract

Micromechanical effects such as the development of crystallographic texture and of dislocation structures lead to evolution of material anisotropy during plastic deformation. The anisotropy of sheet metals is commonly quantified by its R-values. The R-value is defined as the ratio of the transverse strain to the thickness strain at a certain longitudinal strain, and it changes if the anisotropy changes. Conventional hardening models do not account for the evolution of anisotropy along an arbitrary orientation. Therefore, although R-values are measured from experiments, predictions of hardening behavior based on R-values using conventional hardening models do not reproduce the experiments for arbitrary orientation. The R-value evolution for large strains can be observed in simple uniaxial tension tests by measuring the transverse and longitudinal strains continuously up to large strains. A digital image correlation (DIC) method is introduced as superior to strain gages for measuring large strains. To model the experimental response, a rotational-isotropic-kinematic (RIK) hardening model is investigated. Because of this model’s ability to represent the rotational evolution of the anisotropy, it can predict the hardening behavior for non-RD and non-TD directions. Methods to identify the plastic spin and kinematic hardening parameters are also discussed.

Keywords
Anisotropy evolution, $R$-value evolution, DIC measurements, rotational hardening
Milestones
Received: 22 October 2005
Revised: 27 November 2005
Accepted: 30 November 2005
Published: 1 June 2006
Authors
Yangwook Choi
Dr. Yangwook Choi
Department of Mechanical Engineering
The Ohio State University
650 Ackerman Road
Columbus, Ohio 43210
United States
Mark E. Walter
Dr. Mark E. Walter
Department of Mechanical Engineering
The Ohio State University
650 Ackerman Road
Columbus, Ohio 43210
United States
June K. Lee
Dr. June K. Lee
Department of Mechanical Engineering
The Ohio State University
650 Ackerman Road
Columbus, Ohio 43210
United States
Chung-Souk Han
Dr. Chung-Souk Han
Department of Civil Engineering
North Dakota State University
1410 North 14th Avenue
Fargo, ND 58105
United States