Negative jacobian detected

[wajihaahmad]

Hello Respected Members.
I run my simulation, but getting an error message that: is "Negative jacobian was deducted", I change the values of different parameters but every time i get this error.
Given below is attached file,

https://drive.google.com/file/d/1PsqCINg9zhFL8SnywG7B2XoVab0Cicm_/view?usp=sharing

Looking forward
Best Regards,
Wajiha

[maas]

Hi Wahija,

It looks like the problem is with the contact interface. (The model seems to run fine without the contact.) I do notice that you set this up as a transient biphasic analysis. Was this your intention? I ask because I don't see any pressure boundary conditions, which is a bit odd for a biphasic analysis. I also wonder if the sliding-biphasic contact is the correct choice. This contact interface ensures continuity of the fluid flux across the contact interface. If you do not want to model this aspect, then you can just use sliding-elastic.
In any case, I recommend starting with a much lower value for the penalty parameter. Then, you can inspect the resulting penetration and if it is too much, you can then increase the penalty and rerun the model again. Hope this helps!

Best,

Steve

[wajihaahmad]

Hello Steve
Thanks for your reply.

1). I thought that the surfaces which are not in contact got automatically set having fluid pressure equal to zero so fluid can flow through these surfaces, and as the contact surfaces have sliding biphasic contact so that ensures continuous fluid flow across these interface surfaces, so i didn't set any boundary condition for pressure. Pore Pressure and solid matrix deformation (displacement) are my unknowns.
2). As the tendons extensed and flexed(rotated) and i have to see how stress, pressure changes as a result, so that's why i chose transient biphasic analysis.

Best Regards,
Wajiha