| A study has been made of blow forming of 3㎜ thick superplastic 8090 Al alloy sheets into a 6㎝ dia. cylindrical die and a 3㎝ × 9㎝ rectangular die to form a hemispherical cup and plane strain deformation, respectively. Forming pressure-time curves for hemispherical cup forming and plane strain deformation have been analytically calculated using Ragab`s method and Ghosh`s method, respectively, which are based on the membrane theory. The flow curves for calculation of the pressure-time curves were measured at an optimum strain rate. The measured deformation behaviors of the sheets during blow forming in accordance with the forming pressure-time curves have been compared with results predicted by the analytical methods and the elasto-plastic finite element method. The pole height, stress and strain distributions, and thickness distributions of the formed cups are better simulated by the FEM than the analytical methods. |
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