Effect of flow stress - Strain relation on forming limit of 5754O aluminum alloy

A modified Swift type flow stress - strain relation was presented in order to describe the uniaxial tension test curve reasonably. The FLD-strain (forming limit diagram made up of limit strain) of 5754O aluminum alloy sheet was calculated based on the two flow stress - strain relations using Yld2000-2d yield function. By comparing the theoretical and experimental results, it is found that the calculated FLD-strain based on the modified Swift flow stress - strain relation can reasonably describe the experimental results. However, though the common Voce flow stress - strain relation can describe the deformation behavior during homogenous deformation phase accurately, the FLD-strain calculated based on it is obviously lower than the experimental result. It is concluded that the higher the hardening rate of sheet metal is, the higher the forming limit is. A method for determining the reasonable flow stress - strain relation is recommended for describing the material behavior during inhomogenous phase and the forming limit of sheet metal.