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element becomes distorted sometimes, and not other times, why?

element becomes distorted sometimes, and not other times, why?

element becomes distorted sometimes, and not other times, why?

(OP)
Hi,

I am using Patran to auto mesh 4 parts that are in contact with each other.  They have some coincidental surfaces, patran detected that, and I chose to create duplicate surfaces.  I assigned mesh seed on the surfaces by part, and because some surfaces are coincidental, if I assign mesh seed on one part, they will also show up in other parts if the surface show up in both parts.  

This created problems when doing the meshing: locations where mesh seed appear in both parts will only have one node assigned -- which effectively forces the two parts to be tied.  I don't want that, so I use Patran to create mesh part by part, and make sure the node/element numbers for different parts are seperate, no overlap.  Then, I manually combine different input files (node/elem info) into one single file.  

However, it's so strange, that if I datacheck each input file for each part seperatedly in ABAQUS (tried both v6.3 and v6.4), the elements are OK -- there are some warning messages, but no error for highly distorted elements.  But, when I combined different parts together into one file, there are just too many error messages saying that elements are distorted.  Could someone help me what is going wrong?  And, what is the tip to tell patran generate different node numbers for different parts even if they have the same mesh seeds?

Thanks so much!

Sean

RE: element becomes distorted sometimes, and not other times, why?

i guess you must have checked the nlgeom on. turn it off and run the analysis. this might help.

RE: element becomes distorted sometimes, and not other times, why?

(OP)
Thanks, but how?  Where and what should be put in the input file to do that?  Thanks a lot!

RE: element becomes distorted sometimes, and not other times, why?

(OP)
I just checked the manual for *STEP NLGEOM, but no, I didn't have this in my input file, i.e., I have it turned off. :-(

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