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...
If I understand your description correctly, you have to let the dynamics stabilize/relax before turning off the acceleration abruptly.
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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...
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...
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...
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.
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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...
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...
I like Klaus Jurgen Bathe's book. Years after reading his book, I found out that MIT threw an excellent couple of lectures series by him up on YouTube. I found those really valuable.
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Why are you, for lack of a better term, "hung up" on element quality metrics? What are ultimately hoping to achieve? I am asking because, in general, as you refine elements or as deformation occurs, the element quality will change.
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I did not mean to suggest you will need to code a subroutine.
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I have no experience with chip formation modeling so take this with a pinch of salt - FEAway sounds correct to me. At its core, ALE is a generalization of two reference frames - explains the name given to the method. That generalization has nothing to do with specifics of chip formation. I would...
Take a big step back. Make an extremely simple yet relevant problem and test your understanding of the kinematic coupling feature. For instance, create a square or a cube (made up of one or more elements) and a reference node. Then, play with the features. Simple tests of this nature run fast...
I have not used Abaqus in almost a decade but, if I recall correctly, some subroutines get called a couple of times. I think I managed to dig up some PDFs on subroutines online and there was some information along those lines. Take that with a healthy dose of skepticism...
centondollar is exactly right - Whether a scheme is implicit or explicit doesn't matter; you are ultimately solving the same governing equations.
There are a few subtleties that don't concern modelers but are still good to be aware of - 1) Numerical schemes need not be implicit or explicit...
""you can solve a time dependent problem with an implicit code" ... this is quasi-static, with body forces ignored or modelled (as input "loads")."
In principle, you can solve any numerical solid mechanics problem with an implicit code - static, dynamic, viscoelastic, poroelastic, etc. Its...
I can guess but I am not certain about the source of oscillations in the results.
By the way, an implicit numerical scheme has nothing to do with time i.e., you can solve a time dependent problem with an implicit code. Static analysis is an engineering approximation in which "time" is treated...
@rb1957 -
Here is a solver agnostic or a "numerical" description. Regardless of the commercial code you are using, these underlying numerical principles will be true.
Explicit numerical schemes assume equilibrium at t=0 and "solve" the system of equations by marching in time - nothing fancy...
Abaqus/Explicit does not check for or enforce equilibrium so this is not unexpected.
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@muruep00
1) You do not want to think of the mesh without any consideration for what the loading/BCs are and where the gradients of interest are located in the domain. As one good example, consider the following: To capture boundary layer gradients correctly in CFD, highly anisotropic elements...
