Determination of forming limit curves using 3D digital image correlation and in-situ observation

HIJAZİ A. L. A., Yardi N., Madhavan V.

SAMPE 2004, Long Beach, CA, United States Of America, 16 - 20 May 2004, pp.797-809, (Full Text)

  • Publication Type: Conference Paper / Full Text
  • City: Long Beach, CA
  • Country: United States Of America
  • Page Numbers: pp.797-809
  • Keywords: Formability, Optical Testing, Testing/Evaluation
  • Istanbul Gelisim University Affiliated: Yes

Abstract

The use of finite element analysis in process design of sheet metal forming has become a standard practice. Forming limit curves are used in finite element simulations of sheet metal forming to check for possible failure of the sheet. Forming limit curves are typically determined using the limiting dome height test and the strain circle technique. With the development of the three-dimensional digital image correlation technique, it has become possible to determine the forming limit curves with a higher accuracy and less effort typically by comparing images of the test specimens at the end an at the beginning of the test. A limiting dome height tool has been designed such that it permits in-situ observation of the part while it is being formed. Combining in-situ observation with three-dimensional digital image correlation, it is possible to monitor the evolution of strain throughout the sheet from the beginning of the forming to the failure of the sheet. This eliminates the need for an abort criterion since limiting strains can be obtained by considering the deformation stage just before the onset of localized necking. Using this technique, forming limit curves for different aluminum alloys have been determined. The effects of anisotropy and lubrication on limiting strains have also been investigated.