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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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Negative Volume
(@negativevolume)
Guru Admin
Joined: 3 years ago
Posts: 534
 

@ssdng Hmm, it seems the webpage that I originally linked is either down or no longer exists. Let me see if I can track it down for you. 


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Negative Volume
(@negativevolume)
Guru Admin
Joined: 3 years ago
Posts: 534
 

Try this: 

 


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ssdng
(@ssdng)
New Member
Joined: 4 months ago
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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IceBreakerSours
(@icebreakersours)
Regular
Joined: 1 year ago
Posts: 61
 

@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
(@ssdng)
New Member
Joined: 4 months ago
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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IceBreakerSours
(@icebreakersours)
Regular
Joined: 1 year ago
Posts: 61
 

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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