Considerations on the Role of the Actual Blank Holder in the Generation of the Restraining Force 970988

The role of the blank holder in the generation of the restraining forces acting on the metal sheet during the deep drawing is considered. It is well known that the choice of the restraining force distribution is a key point in the definition of the stamping process.
The evolution of the blank holder modelling in the finite element simulation of the drawing process is reviewed and the need of deformable model of the blank holder to obtain process realistic simulation is pointed out.
The factors that affect the actual restraining force distribution are briefly analyzed, identifying control factors (that are at disposal of the process engineering in order to tune-up the actual tool) and noise factors (that are not practically controllable).
In order to have a realistic numerical simulation of the drawing process, these factors have to be included in the finite element model, with particular attention to the different alternatives for the blank holder modelling. It is shown, that in some cases, a deformable model of the blank holder is needed in order to obtain a realistic description of the restraining forces distribution.
A diagram showing the allowed range of variation of the restraining force distribution can be obtained and the process engineer can verify the robustness of the process, taking into account the outlined variation of the noise parameters.


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