help with adding MPC in keyword editor

[bebme]

I am trying to use the Quadratic multipoint contraint in order to reduce the amount of elements in my model. So I am trying to go from a fine to a course mesh, but I am unsure of where to add this MPC constraint within the keyword editor. In the ABAQUS/Standard tutorial, for the cargo crane example, they added the MPC within the assembly option block, right before the *end assembly keyword line. I try to do that also using the nodes assigned from the once I meshed my assembly, but I get errors saying surface and element sets are unknown and dont exist even though in the lines above where I entered the MPCs, the element sets, instances, and surfaces are defined. Anyone have an idea what I am doing wrong. Thank you

 

[bassmanjax]

If you are using part instances in the assembly, make sure that you are referencing the node and element sets correctly. Node/element sets created in the part or instance must be referenced by prefixing the instance name.

Regards

Martin Stokes CEng MIMechE

 

[Yoman228]

Wonder if the Tie surface work as well as MPC in this case?

 

[bebme]

Thanks bassmanjax. So would I have to go into keywords, define the nodes that were automatically generated from the meshing feature that I want constrain before the *end part line, then define the quadratic MPCs? The users manual describes how the MPCs should be written, but if the ABAQUS CAE preprocessor generates the nodes, wouldnt they already be defined?

 

[bassmanjax]

I wouldn't even bother with the keyword editor in CAE. Write the input deck from the job module and add the *MPC keywords by editing the .inp file in your favourite text editor. CAE generates a fairly 'untidy' .inp file though - can be hard work trying to decipher it at times...

Alternatively, like Yoman228 said, you may get just as good a result using tied surfaces instead. These are supported in the Interaction module in CAE.

Regards

Martin Stokes CEng MIMechE

 

[bebme]

I tried modifying the input file, but it seems that whenever I modify the input file (same goes for keywords editor), the defined parts and surfaces are empty. However, without my additions, it runs fine. Is there something I am missing as far as making corrections to input files? I included the input file that doesnt get processed.

 

[corus]

When ever you define loads/interactions with picked sets and then go back and modify the part or assembly then you can lose sets. Go back to the loads/interaction modules and check that all the definitions are correct.

Also, the keyword editor in 6.7 doesn't appear to work now and you have to edit the .inp file manually. Do they check software before the issue it or wait for the customer to find the bugs?

corus

 

[bebme]

heres my input file I changed manually. So I should load the input file then re-define the parts and surfaces before I run the problem?

 

[corus]

You have picked sets in the data. It's best to check them in CAE and recreate the .inp file under a new name. Use Winmerge, or something else, to compare the old and new files so you can simply transfer any edits across.

corus

 

[1984alpha]

I've the same problem too, I happen to have used MPC Beam for creating a rigid body between the nodes of composite shell and a supporting beam at the edges but when I load the notepad edited .inp file and run the analysis the job aborts with erros and the new .inp file written for the analysis doesn't include my *MPC, BEAM definitions and the composite shell layup.

How can i retain the MPC definitions during the analysis?

Can someone please look at my input file and help me out, you'll realize that when you load the input file, the composite layup disappears, but the beam section definition remains.

 

[bebme]

Thanks Corus,
So I added my MPC to the input file and saved it as a new name. Then imported the model in ABAQUS. It gives me a warning message:
WARNING: The following keywords/parameters are not yet supported by the input file reader:
---------------------------------------------------------------------------------
*MPC

So I guess it turns out v6.7 might not support MPC. Corus, have you made it work before?

 

[bebme]

It seems when you load input files with MPCs into ABAQUS, the MPC command is not yet supported by version 6.7. I am assuming the command is still passed on to the Analysis algorithms even though it does not show up in the submitted input file. The command seems to be functional when you try running one of the MPC examples in the ABAQUS verifications manual. Thanks for your responses guys!