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Recent content by IceBreakerSours

  1. IceBreakerSours

    UMAT subroutine for SMA

    As mentioned by FEA way, there is a supported superelastic material model for Abaqus so why are you looking for a SMA UMAT to use with Abaqus? What limitations does the currently supported superelastic model have? Given that you are looking online and assuming you really need a new SMA UMAT...
  2. IceBreakerSours

    Error When Calculating Minimum Stable Time Increment for Bottom-up Mesh

    Those high quality meshes aren't recreated from medical imaging scans; they are built from 2D wire-frame designs and then mapped to 3D
  3. IceBreakerSours

    Stent Meshing using Tet Elements

    Algorithms to compute centerlines using CG (computational geometry) libraries are available in various packages (CGAL, for sure). However, if you are not a power coder, I wouldn't recommend going down that pathway. A simpler route might be to look at 3DSlicer; it has a VMTK plugin for computing...
  4. IceBreakerSours

    ABAQUS Dynamic Explicit: Stent Crimping

    For a simulation of this level with explicit, I would want to start seeing data trickling into the output file within minutes and the job finished within a few hours. Implicit is a different beast altogether - It will take fewer time steps but the time step size can be much larger compared with...
  5. IceBreakerSours

    ABAQUS Dynamic Explicit: Stent Crimping

    1. 10^-10 is a very small time step. How long (real physical time) are you running the analysis? 2. Once you are past method development and have the analysis running, that time step will still take the job to run to completion. At this early stage when are developing a method, you'll end up...
  6. IceBreakerSours

    ABAQUS Dynamic Explicit: Stent Crimping

    Unrelated - It appears that you have imaged a stent and are using the scan (STL) as a starting point for your mesh - Is that correct? If yes, it would be much better to come up with a much more coarse mesh because the elements may be very small which kills the explicit time step. Also, what is...
  7. IceBreakerSours

    ABAQUS Dynamic Explicit: Stent Crimping

    Have you run explicit analyses before? Do you know if your stent is sufficiently constrained? Not sure why you have multiple rigid plates; usually, these sims have a cylinder with BCs specified in a radial coordinate system. Take a big step back and ensure: 1) BCs are applied as you expect in a...
  8. IceBreakerSours

    Contact control automatic stabilization

    Your method of diagnosis is incorrect. We have to keep the mechanics front and center, make sure the numerical methods approximate the mechanics as best as possible, and identify/isolate where/why/how/.. the numerics are breaking, and then come up with fixes. Your current method will lead you to...
  9. IceBreakerSours

    Contact control automatic stabilization

    If I understand your description correctly, you have to let the dynamics stabilize/relax before turning off the acceleration abruptly. ********************************************************* Are you new to this forum? If so, please read these FAQs: http://www.eng-tips.com/faqs.cfm?fid=376...
  10. IceBreakerSours

    Contact control automatic stabilization

    I think things like stabilization, springs, etc. are fine to use in some cases but clever as they might be, in general, they are numerical tricks. I prefer taking inertia into account and avoiding the instabilities altogether. Friction does result in an unsymmetric tangent stiffness matrix so an...
  11. IceBreakerSours

    ABAQUS: Model not converging after turning on NLGEOM (Even with very small steps)

    1) Start from scratch - Are the units consistent? Are the input "numbers" correct? 2) Build complexity in a step-wise manner - i.e., the baby steps strategy. Ensure something is working, you understand how a key feature works, and add complexity one layer at a time. 3) Since you find yourself...
  12. IceBreakerSours

    Abaqus user subroutine problem

    Given your slow progress so far in nearly 3 weeks when it should not take more than an hour or so, I suggest you ask your supervisor to pay for tech support. Otherwise, you will end up spending way too long on something no one is going to give you credit for i.e., you should be writing code...
  13. IceBreakerSours

    Abaqus user subroutine problem

    Did you manage to successfully execute a job from one of the examples in the documentation? If not, then you might want to give that a try. If that fails, then odds are you have software compatibility issues to fix. ********************************************************* Are you new to this...
  14. IceBreakerSours

    Wedge elements

    Tets are awful, sure. However, if the goal is to automate workflows that involve challenging (e.g., organic/3D-printed) geometries without sacrificing accuracy, there isn't a whole lot out there that can replace those awful tets. The trade-off is to throw lots of tets, let the hardware do the...
  15. IceBreakerSours

    How to validate obtained tangent matrix in isotropic linear hardening

    I am assuming you have an analytical expression for the tangent stiffness matrix. If not, then you may wish to consider using a symbolic math package for that purpose. Then, under simple BCs, predict what the results ought to be from the analytical expression and compare the prediction with...
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