An Analytical Model of the Superplastic Bulge Forming of Sheet Metal

摘要

This paper presents analytical and experimental study on the superplastic bulge forming of hemispherical shell. Most of the simple engineering models proposed to date do not consider the stress and strain variation from apex to the periphery of the bulged shape, although its effect in the calculations of the thickness distribution is well understood. An analytical model is formulated on the basis of the incremental strain theory of plasticity and non-equal biaxial stress states in deformed shell. Simulation programs were developed to predict some deformation parameters such as stresses, strains and thickness distribution, bulging time, pressure-time cycling for constant apex strain rate deformation. In addition to the analytical calculation, Finite Element Analysis (FEA) was conducted to examine the validity of the present analytical model. Bulge forming experiments were conducted by using Ti-alloy "SP-700" sheets of thickness 0.75 mm under Ar gas pressure at the temperature 800 ℃. The suggested model showed good agreement with the experiments and FEA.