Dears, I confront some errors in abaqus for End Notched Flexture test on a composite beam with a precrack.
There are 2 :
The first is ((The system matrix has 3 negative eigenvalues)) during my running,
and the second is under displacement or load, the beams can not be propagated from the initial crack region and the run is being interrupted.
Does anyone have any suggestions to solve these issues?
Thank you so much
Dear mohammadreza
For the first issue:
assume that you're running an standard solver.There are many reasons for the constant negative eigenvalue warning including: incompatible units, incorrect property definition, unreal boundaries or loads, incorrect interactions and mesh size. However, for the cases like large unreal loads or large element sizes, the software usually tries to prevent it by decreasing the step time and therefore , converge, unless the issue couldn't be corrected by this method.
So in conclusion, eighter your model definitions are incorrect somewhere or the step time is too big to converge.
And for the second:
Can't understand your question properly. What does "interrupt" means here? Do you get errors and the job get terminated?if so, what the error says? Did you define the precrack and the relevant definitions correctly?
Mohammadreza Mohaseb Karimlou In dealing with Abaqus, students act like it is a boxing match, it's not a boxing match; it's a conversation make sure you're speaking the same language (Input units, material properties and so on). I am kidding, by the way, I think the two errors you are facing are related. The first error is indicating that the system matrix has negative eigenvalues, which is a sign of instability. This can be caused by a number of factors, such as incorrect material properties, boundary conditions, or loading conditions. The second error is indicating that the beam cannot be propagated from the initial crack region, which is likely due to the instability in the system.
To solve these issues, you should first check your material properties, boundary conditions, and loading conditions to make sure they are correct. You may also need to adjust your mesh size or use a different element type.
Mohammad Noruzi Dear Mohammad, I'm really thankful for your response. In fact, I modified some boundary conditions while I have still those sorts of Eigenvalues during bending applied. I suppose there is nothing that would sublimely need to change or be wrong. I am suspicious about the meshes. Do you have any suggestions to me? What about hourglass? Should I change something in the hourglass settings in module Mesh?
My model is Solid and 2 supports (roller and pinned located in each inner sides and a displacement applied from the top.
About your question: Yes, there is also a precrack and crack definitions (including debonding)
Engr. Tufail Dear Tufail, Thank you so much for the description. I described something for Mohammad and I will put it below again:
In fact, I modified some boundary conditions while I have still those sorts of Eigenvalues during bending applied. I suppose there is nothing that would sublimely need to change or be wrong. I am suspicious about the meshes. Do you have any suggestions to me? What about hourglass? Should I change something in the hourglass settings in module Mesh?
My model is Solid and 2 supports (roller and pinned located in each inner sides and a displacement applied from the top.
There is also a certain precrack length for the specimen.
Hi Mohammadreza,
Would it be possible to provide a picture of your mesh and boundary conditions?
Regards,
Simon
Simon Smith Hello Dear Simon,
Thank you so much for your concern and for following it up.
Fortunately, at the moment, my problem is solved.
Again, I appreciate you.
Hi Mohammadreza,
How to solve the problem of the Negative eigenvalue in your model?
I have the same problem in my model.
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