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Monday, December 10, 2018
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Interaction of COPRA® RF DTM and COPRA® FEA RF

COPRA® RF DTM is the missing link between the COPRA® RF  software program and Finite Element Analysis programs. The latter is, however, providing more and better results (especially in terms of forces, torques or deformations of the profile), but due to the high computing time required by FEA programs this intelligent "pre-processor" COPRA® RF DTM allows for a fast optimization of the tooling geometry even before starting any time consuming Finite Element calculation.
COPRA® RF DTM and COPRA® FEA RF are not substituting each other but complementing in an ideal way.
Following graph is explaining the interaction between COPRA® RF DTM and COPRA® FEA RF:

The simulation calculation is being performed inside of the COPRA® software package. The DTM module is providing the complete visualization of the forming sequence. In addition the user gets shown diagrams with information about theoretical maximal and actual deformations in the most critical areas. This allows for an accurate and fast estimate of the design's quality.
Undesired effects like exceeding elongation values or even compression areas can be identified by means of the simulation model. The calculation results give answers on areas having most probably too high plastic deformations and show whether the material is getting stretched homogenously, e.g. without peaks, throughout the roll forming mill.
Questions if intermediate passes could be helpful or just to determine the optimum position of a profile in the mill can be answered easily.
For the tooling engineer it is of importance to learn about critical passes before starting the tool design or even -manufacturing.
If a profile has to be punched or notched he can make sure that especially these areas will have reduced longitudinal strain- and reduced stress values. This reduces any misshape of punched patterns.
Based on these results the tool designer is able to modify respective forming steps accordingly and to detail the roll tooling. He will be able to compare different forming strategies and methods against each other and to choose the optimum forming method in terms of machine requirements and/or product quality - without causing any tooling costs and wasting setup time.

Plastic strain values:

From COPRA® RF release 2003  the user of COPRA® RF DTM  does not only get graphs and diagrams showing residual strain values on the profile's cross section (on top or bottom surface) in each forming stand but also the accumulated plastic strain values. This feature takes into account the permanent deformation (possible yield of material) in each forming stand and the elastic recovery in longitudinal direction after the forming pass. The accumulated value give an idea about how much the material it getting overworked and how much remaining formability the final product is going to have. The following diagram (done by COPRA® FEA RF) explains this effect:

COPRA® FEA RF: the blue curve shows the accumulated longitudinal plastic strain values on the top surface of strip edge on a 3 step example:

COPRA® RF DTM: the blue curve shows the theoretical strain values (left picture) as well as the theoretical plastic (permanent) strain values (right picture) at - in this example) the strip edge. It has to be noted that the roll tool diameter is having a major influence on respective result.