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Convergence prevented due to unfulfilled bc...

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(@pauriera)
Unpaid Intern
Joined: 2 years ago

Hi there,

I am working on a simple model of a 3-point bending test of a plate, where I have a metallic, rectangular plate on the bottom, followed by an adhesive and an adherend on top of it. All the materials are modeled with solid elements and MAT_001_ELASTIC and MAT_138 for the adhesive. The left and right edges of the plate are clamped and I am applying a static displacement over a small area in the center (the figure is just a quarter of the plate, to exploit symmetry), and therefore I am using the implicit solver (also working with a reasonably large timescale). However, at some point, I get the error message "Convergence prevented due to unfulfilled bc...", which I am unable to understand, and that leads to a fatal error " Nonlinear solver failed to find equilibrium". If I change the adhesive material to MAT_001, it seems to work but I cannot resolve the issue using MAT_138... Is there any way around the error? And where is it coming from? I would really appreciate some insight here! Many thanks in advance!

 model
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Negative Volume
Posts: 639
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(@negativevolume)
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Joined: 5 years ago

Hi @pauriera

Sorry for not getting this answered for you. You probably solved this by now but it sounds like you had issues with the Implicit convergence in combination with this *Mat_cohesive_mixed_mode material. If it worked fine switching that material to elastic, then there is either something wrong in your material parameters of that *Mat_138, or that material is causing difficulties for dyna to find convergence which might mean that you need additional settings for your Implicit solver. Reading through the material manuals of dyna can usually help clear up confusion with these more complex materials and this link below can help debug issues with convergence in implicit. 

https://www.dynasupport.com/howtos/implicit/implicit-convergence

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