Negative Jacobian error message on Modal Analysis

[natedawg88]

Every time I attempt to run a modal analysis on my model I get the error message:
* * * E R R O R * * * (WHILE RUNNING ANALYSIS)
NEGATIVE JACOBIAN ENCOUNTERED,
CHECK ELEMENT CONNECTIVITY AND JOINT COORDINATES FOR ELEMENT 21491

I have checked and this element has 8 points all of which are correct and shared with the appropriate amount of other nodes. Additionally the volume is positive for the element so that cannot be the problem. Anyone had this error before or have any ideas of what I can do to fix it?

Thanks in advance

 

[natedawg88]

Nevermind. I finally figured it out. Sorry for the inconvience.

 

[popabf]

Well, tell the others what was the problem so they can learn from your mistakes. It would be a generous gesture.

 

[natedawg88]

Sorry. It was simply that the element I had created was skinny enough that one node was outside of the line between two other nodes. This basically created a negative volume in one portion of the shape. Thus, while the overall volume of the elemenet was positive and the nodes were all connected in the correct order the shape of the element was still not valid. I hope this makes some sense but it is hard to explain without pictures.