Hi all, in most all simulation I do with glue/contact constrain, there are a few warning messages show in the dialog
NASTRAN Msg: *** USER WARNING MESSAGE 4690 (CNTGAPERR) The gap between glue faces of some elements in gap pair 2 between NASTRAN Msg: *** USER WARNING MESSAGE 4690 (CNTGAPERR) The gap between glue faces of some elements in gap pair 4
I do not understand what does it means by gap in gap pair. Can anyone explain to me what it means? However the result of the simulation looks normal even with these errors, so are these error important or not?
Solved! Go to Solution.
If the gap between the source face and target face is greater than a certain percentage of the source face maximum edge length, nastran outputs the CNTGAPERR message. This means the gap between source face and the target face is probably significant and needs to be looked into by the user
If the refinement is turned ON which is the default, nastran refines the source face into triangles. In this case, nastran looks into the triangle size and compares it with the gap size. In many instances the gap size becomes comparable with the triangle edge size since these are much smaller than the source face. In this case, CNTGAPERR prints out "FALSE POSITIVES". You can then safely ignore this message.
To make sure that the messages are indeed false positives, you can run the nastran job by turning off the refinement. If you still get the CNTGAPERR you might want to make sure that your search distance is not too big.
If you are running linear contact problems, initial search distance can play a significant role in performance.
For gluing, it is typically assumed that the gap between the source and target is reasonably small. If there is a large gap between the source and the targe, gluing is still valid. However, physically gluing surfaces far apart might not be physically reasonable (what fills the gap between the surfaces?) or user intended. The message just informs the user to take a look and see if the gap is large to make sure they did not make a mistake with search distance.
Simply put, large gap distances means that you are connecting two surfaces unreasonably.