Large Strain Cruciform Biaxial Testing for FLC Detection


20th International ESAFORM Conference on Material Forming, Dublin, Ireland, 26 - 28 April 2017, vol.1896 identifier identifier

  • Publication Type: Conference Paper / Full Text
  • Volume: 1896
  • Doi Number: 10.1063/1.5007975
  • City: Dublin
  • Country: Ireland
  • Middle East Technical University Affiliated: Yes


Selection of proper test method, specimen design and analysis method are key issues for studying formability of sheet metals and detection of their forming limit curves (FLC). Materials with complex microstructures may need an additional micro-mechanical investigation and accurate modelling. Cruciform biaxial test stands as an alternative to standard tests as it achieves frictionless, in-plane, multi-axial stress states with a single sample geometry. In this study, we introduce a small-scale (less than 10 cm) cruciform sample allowing micro-mechanical investigation at stress states ranging from plane strain to equibiaxial. With successful specimen design and surface finish, large forming limit strains are obtained at the test region of the sample. The large forming limit strains obtained by experiments are compared to the values obtained from Marciniak-Kuczynski (M-K) local necking model and Cockroft-Latham damage model. This comparison shows that the experimental limiting strains are beyond the theoretical values, approaching to the fracture strain of the two test materials: Al-6061-T6 aluminum alloy and DC-04 high formability steel.