Vincent Shebib Loiselle

***CRITICAL WARNING*** for NON-TOUCHING FACES bonded contact and SHEET METAL ANALYSIS

Discussion created by Vincent Shebib Loiselle on Sep 27, 2017
Latest reply on Nov 23, 2017 by Thierry Ouellet

Hi,

 

I realized that making a bonded contact between non-touching faces or edge using the 3 following techniques could produce wrong result :

 

  1. "Non-touching faces" option in component contact
  2. Using the mid-surfaces that are automatically generated when starting a Sheet metal analysis
  3. Using contact set between distant sets

 

All those techniques could produce wrong result because the relation written between distant sets is false. This relation is displacement equality and rotation equality between the nodes or elements in the sets. This erroneous relation between distant sets locks the rotation of the model at bonded contact points. Sometimes the impact is low, but something it could be crazy high.

 

In my static simulation (I can't put it online) the deformation was 18 times underestimate when using the automatic mid-surface shells analysis with sheet metal parts.

 

I'm joining 3 other cases to show the problem.

 

It's been a mouth I'm trying to explain the problem to technical support... And it is still going. I think it is a failling bridge issue and it needs immediate care.

 

I see 2 options :

 

  1. Putting a warning every time the solver is started with a non-touching bonded contact condition. This warning should be linked to a well explained help page that will explain in what kind of study we are likely to have errors and that it is more accurate in every case to use touching extended mid-surface shells or touching offset shells.
  2. Removing all those non-touching bonded contact options from the software, those could create failing bridges.

 

 

This problem is also related to transmission of shear between distant bonded shells and the SPR #:464938. It's the same wrong relations that creates the problem.

 

Is someone having more examples or infos on this error ?

Do you also think SW should have a fast fix to inform Users ?

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