×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Negative Jacobian error message on Modal Analysis

Negative Jacobian error message on Modal Analysis

Negative Jacobian error message on Modal Analysis

(OP)
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

RE: Negative Jacobian error message on Modal Analysis

(OP)
Nevermind. I finally figured it out.  Sorry for the inconvience.

RE: Negative Jacobian error message on Modal Analysis

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

RE: Negative Jacobian error message on Modal Analysis

(OP)
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.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources