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  1. Hi, A reference that says the stiffness matrix...

    Hi,

    A reference that says the stiffness matrix should positive definite can be found here.
    Under finite deformation biphasic problems converge better if you use full Newton iterations (max_ups=0)...
  2. Hi Shamimur, The two constitutive models are...

    Hi Shamimur,

    The two constitutive models are different and you can look up their exact form in the User's Manual. Which one you should use depends on which experimental cartilage data you want to...
  3. Hi Carly, I looked at your model and here are...

    Hi Carly,

    I looked at your model and here are the things you need to modify:

    1) The pulmonary artery mesh is not hollow, which means that there is no inner wall against which the stent can...
  4. Hi Carly, Yes, you can email me the file (or a...

    Hi Carly,

    Yes, you can email me the file (or a link to it): ateshian@columbia.edu.

    Best,

    Gerard
  5. Hi, If you could create a smaller model that...

    Hi,

    If you could create a smaller model that re-creates your problem and share it, that would be helpful. Otherwise it is hard to figure out if this issue is related to the mesh, material...
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    You can download the converted files from...

    You can download the converted files from https://www.dropbox.com/s/snn1po65hb82b70/Archive.zip?dl=0.

    Regarding your linux server, please try both versions of the executable available on the...
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    Hi Fluvio, The short answer is yes, of course...

    Hi Fluvio,

    The short answer is yes, of course you could think of it like that. The more detailed answer is that this normal displacement constraint is a non-standard condition that you have...
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    Hi Fluvio, The normal displacement constraint...

    Hi Fluvio,

    The normal displacement constraint gets enforced very strictly with higher penalty parameters. In a numerical scheme with finite time steps, what would normally be a tangential...
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    Hi Fluvio, I am glad it's working :) The...

    Hi Fluvio,

    I am glad it's working :)

    The penalty I chose was not based on any of the properties of the materials in the model. Basically I ran the analysis with 1, 10, 100, then jumped to 1e5...
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    Hi Tres, Fulvio, I went over your code and...

    Hi Tres, Fulvio,

    I went over your code and found one bug and one omission:

    (1) Bug: in FEFixedNormalDisplacement::StiffnessMatrix, FESurfaceElement& el = m_s.Element(1); should be...
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    Hi Fluvio, If you send (or share with) me your...

    Hi Fluvio,

    If you send (or share with) me your full code, I can take a closer look.

    Best,

    Gerard
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    Hi Fluvio, In the double loop, please keep in...

    Hi Fluvio,

    In the double loop, please keep in mind that 'a' is the same as 'i' and 'b' is the same as 'j'. So you should use
    kab = (U*A*N[i] + N[i]*N[j]*Nu*da)*w[k]*m_eps;
    Please delete the...
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    Hi Kiera, The current version of FEBioStudio...

    Hi Kiera,

    The current version of FEBioStudio is in beta. You may have to toggle the Material Axes a couple of times, hopefully that should work.

    Best,

    Gerard
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    Hi Fluvio, Your code for the residual seems...

    Hi Fluvio,

    Your code for the residual seems correct. You can delete the line that includes double p = m_s.m_p; since it is not needed here.

    Also (and this was my mistake when I said the rest...
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    Hi Kiera, I have attached the C++ code (2170)....

    Hi Kiera,

    I have attached the C++ code (2170). The dimensions of the ellipsoid are hard-coded using the formulas from the paper by Land et al. , see their equations 2.6 through 2.12. If you need...
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    Hi, Are you using a structured mesh (e.g., hex...

    Hi,

    Are you using a structured mesh (e.g., hex elements that form multiple layers transmurally) or an unstructured mesh (e.g., tet elements)?

    Also, please take a look at a Case Study we posted...
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    Hi Fluvio, dxr and dxs in the code correspond...

    Hi Fluvio,

    dxr and dxs in the code correspond to g1 and g2 in the derivation, respectively. v in the code corresponds to g1 x g2 (not n) in the derivation in addition to being multiplied by the...
  18. Hi Will, You can verify that equation (4)...

    Hi Will,

    You can verify that equation (4) satisfies equation (2) using Mathematica. I have attached a screen shot of the verification.
    2158

    Let me know if that answers your concern.

    Best,...
  19. Hi Hao Dinh, I took a quick look and it seems...

    Hi Hao Dinh,

    I took a quick look and it seems you are using a fluid-FSI model (since your finite element domain includes fluid-FSI and neo-Hookean materials), but your analysis type is Fluid. You...
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    Hi Shamimur, I looked at the file you sent me...

    Hi Shamimur,

    I looked at the file you sent me and here are a few things I needed to do to make it run to completion:

    1) You have two steps, the first is steady-state swelling and the second is...
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    Hi Shamimur, Yes, you can email me the model...

    Hi Shamimur,

    Yes, you can email me the model if you are unable to post it on the forum. Please keep in mind that it is harder and more time-consuming for me to examine very large models, so...
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    We expect to release FEBio3 and FEBioStudio in...

    We expect to release FEBio3 and FEBioStudio in July. An exact date has not been set, as we still need to finalize a few things and make sure that FEBio3 runs the same as FEBio2 for all of the test...
  23. Hi Hao Dinh, If you set prescribe the fluid...

    Hi Hao Dinh,

    If you set prescribe the fluid dilatation to zero at the outlet (equivalent to zero fluid pressure), and you don't prescribe any velocity boundary conditions, the flow can go through....
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    Hi Tres, Fulvio, We have not yet officially...

    Hi Tres, Fulvio,

    We have not yet officially released FEBio 3.0, which is why, to the best of my knowledge, the SDKs are not yet available.

    We hope to release FEBio 3.0 in July. If you would...
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    https://www.dropbox.com/s/m70cnhldobhwu0j/Archive....

    https://www.dropbox.com/s/m70cnhldobhwu0j/Archive.zip?dl=0
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