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I am tying to solve a non-linear problem using Ls-Dyna IMPLICIT solver. However, I am unable to achieve convergence.

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Posts: 5
(@delcon)
Unpaid Intern
Joined: 4 years ago

Also on last steps before failure this message:

"convergence failure, repeat step: dtnew = 2.78495E-02"

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Negative Volume
Posts: 665
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(@negativevolume)
CEO
Joined: 6 years ago
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(@ssdng)
Joined: 3 years ago

Barista
Posts: 3

Hi @negativevolume,

Thankyou for sharing the file. I wonder if you could help me solve my problem. I get an error stating:

line contains improperly formatted data reading *CONTACT_OPTIONS card. ( for OPTION CARD C)
On *CONTACT_SURFACE_TO_SURFACE
I am trying to simulate static analysis for concrete pipe under displacement load. So if I used option A and B only for *contact_surface_to _surface, I end up getting "non-linear solve failed to find equilibrium'.

I would appreciate any suggestion to get the converged result.

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Posts: 61
(@icebreakersours)
Lab Tech
Joined: 4 years ago

@ssdng Is the physics statically indeterminate? Does the solver get past a few time steps before quitting or does it quit without ever converging the first time step?

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(@ssdng)
Joined: 3 years ago

Barista
Posts: 3

Hi @icebreakersours 

When I use option A and B only for *contact_surface_to _surface,  the solver does get past for few hours before showing termination error.

But When I use option A, B and C for *contact_surface_to _surface,  the solver shows termination error indicating problem with contact option C. I have used Igap 2.

I also tried a case with *contact_automatic_single _surface, for this the analysis do get complete but its false one as load doesn't get transferred via master to slave.

And for *contact_surface_to _surface with out any option card, I get warning about negative eigen value. I tried to incorporate suggestions in discussion on using erode. but it didn't help.

I would really appreciate if you could suggest me with this contact issue.

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Posts: 61
(@icebreakersours)
Lab Tech
Joined: 4 years ago

Why does the solver quit after those few hours when you use option A and B?

I am seeing: "I played with this knob and it crashed. I played with that knob and it crashed. .. ..". Put your detective cap on and try to understand what is going on when you change knobs. Finally, mechanics/physics comes first (not the numerics) i.e., without an understanding of what is happening, there is no hope of diagnosing the symptoms and coming up with the right medication.

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