Moreover, to prevent wrinkling in the sheet drawing process, a blank holder pressure up to 15 bars, during the forming process was applied over blank holders for each case.
For meshing of tools (punch, die and blank holder), 2-node linear axisymmetric rigid link elements (RAX2) were used.
Because of the ironing process was occurred in end of drawing, Shell elements or Membrane elements were not suit for meshing of sheet and have been gave illusive results.
Hence, 4-node bilinear axisymmetric quadrilateral solid element with reduced integration (CAX4R) was used for meshing of deformable sheet. On the other hand, central area of blank was not critical in deep drawing analysis; therefore meshing size in central section of blank was greater than other sections to reaching the less time for analysis.
Sheet meshing is illustrated in Fig. 4.
A deviating shape is caused by elastic springback after forming and retracting the tools.
Therefore, the entire 4-step drawings have been solved including springback after each
drawing step.
Spring back is simulated through an implicit calculation which is solved with the aid of ABAQUS Standard.
The deformed shapes for each step and plastic strain values of them as color contours are shown in Fig. 5.
It is necessary to say the annealing operation was performed after second step, therefore to simulation of annealing operation in ABAQUS software, an orphan mesh was imported to third step from final drawn part in second step.
This operation nullified stress and strain history.
Experimental results are included thickness distribution of deformed parts in any steps, and have been extracted by measuring of wall thickness in various points on produced parts.
These results has been presented in next section and then compared with FE simulation results.