Search
Close this search box.
Notifications
Clear all

NEGATIVE EIGENVALUES Problem in Abaqus

3 Posts
3 Users
0 Likes
1,246 Views
Posts: 13
 Mahy
Topic starter
(@Mahy)
Active Member
Joined: 8 years ago

Dear all,

I am modeling a 2D concrete element in abaqus with user subroutine UMAT in which I defined an isotropic damage model. The element is constrained in the bottom edge, and displacement applied in the top edge.

The analysis is completed but there are a lot of error message say that THE SYSTEM MATRIX HAS NEGATIVE EIGENVALUES. Morever, I get a strange curve which does not represent the softening behavior of the concrete.

Can anyone help me ?

Thank you.

Topic Tags
2 Replies
Posts: 2
(@sparkle)
New Member
Joined: 9 years ago

What i am undetstanding you are trying to find out buckling modes.....for this u can provide minimun eigen value while defining step.....

Topic Tags
2 Replies
Posts: 6
(@LennonCauser)
Active Member
Joined: 9 years ago

I think that kind of error is related to the incompressibility constraint.
A good idea is to include an stability verification into the UMAT . That is, check if the determinant of DFGRD1 is between two predefined values. Case not, set a new value to PNEWDT and return to a new iteration.

Reply
Share: