Figs. (6)-(9) provide a comparison of the sheet-thickness distribution after drawing for numerical simulations and forexperiments.
It is intelligible from comparing of simulated results with experimental data so that the FEM predicted trends for all of the cases are in good agreement with experimental data.
However, in some of points such as punch corners have errors and these errors have been increased in third and fourth steps.
It is because of changes in plastic behavior of initial sheet due to work hardening.
This condition is not considered in simulation analysis.
Therefore, errors are increased in these cases.
Maximum error in this simulation is up to 10%.
The diagrams of sheet thickness distribution confirm the FE simulation is to be authentic.
Therefore, other simulation results such as punch forces for any step have been extracted from finite element analysis.
In Fig. 10 maximum punch force for any drawing steps has presented and compared with that from generally accepted formula for predicting maximum punch load at die design literatures [10].