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(OP)
I am trying to mesh a solder joint. As a first step in that dierction, I am working on a simple problem.

The model consists of two plates, a copper palte and a steel plate. I want to have a perfect contact/joint between the two.

I want to load this bimetallic model amd see the stress and strain distribution.

I have used the plate elements and also checked for coincident nodes and merged them.

I still end out getting fatal errors.

Any ideas/pointers in the right direction?

Thanks

If you defined two sets of plate elements connected with coincident nodes, you should not have gotten any fatal errors.  I suspect that your fatal error is due to some other problem not related to the coincident nodes.  One problem with this modeling technique is that you will not be able to see displacement coupling between the two plates since their mid-planes are coincident.  Try the following modeling technique to work around this problem:

Define two surfaces, one at the mid-plane of the copper plate and the other at the mid-plane of the steel plate.

Develop an identical finite element mesh for the two surfaces.

Connect rigid elements between each corresponding node on one plate to the corresponding node on the other plate.  These rigid elements should be defined in all degrees-of-freedom except for the normal plate rotation.

Place constraints and loads on both of the plates and run your analysis.  Note that you should not place a constraint on a node that you have already defined as a dependent degree-of-freedom with a rigid element, as this will result in a fatal error.  You should only constrain the independent degrees-of-freedom on the rigid elements.

pj

Pj is right, you can try that. What you can also do is renumber your mesh and try again the equivalencing, but with a higher tolerance.
Are u sure u didn't make any construction errors, like deleting an element without all its associated nodes ?
You have to be very carefull when using MPCs, and one useful trick to make the system work with this feature is to employ a "plate Rz stiffness factor" (which is in fact the drilling stiffness) in your solution parameters. As english is not my native language, I don't understand clearly your load / restaint set up ... and u may not need a drilling stiffness. But just in case, if u use it, be sure that your results are not "widely influenced" by that (try a sensitivity study or something like that).
Don't connect two MPC together as u will come up with fatal errors ... use a bar element between if u need to connect MPCs together.
Have fun !!
nico 68
(If u can explain your pb in french, I'll probably be able to answer more clearly ...)

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