| The results from a study of the numerical prediction of limiting draw ratio (LDR) are presented. A series of ten different tooling geometries were considered for a cylindrical cup drawing process, with the differences being variations in the die and punch profile radii.; A validation study in which numerical predictions were compared with experiments was performed on six different tooling geometries. These studies demonstrate that the numerical model accurately captured the forming process. The punch forces, blank draw-in, and strain history are found to be in reasonable agreement with the experiments. Some concern exists that the friction coefficient used was somewhat low as indicated by predicted major strains in the wall being consistently lower than measured.; The choice of anisotropic yield criterion was shown to have a strong influence on predicted strains. The numerical model somewhat overpredicts LDR for 6-12 mm profile radii due to the use of a low coefficient of friction. If the data were available to support an increase in friction coefficient, then the model would lie in better accord with the experiments. For the sharp, 3 mm die radius, the model largely over-predicts LDR (unconservative) which suggests a change in failure mechanism, to a bending failure, since the bend radius to thickness ratio approaches the bendability limit for AA5754-O. |
