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In reply to Abaqus system error code 1073741511
I recommend you become a member of the ABAQUS mailing list
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I know what Simulia HQ is watching closely. Someone from HQ replied to one of my postings a couple of years ago in the context of a misprint in the manual
Congratulations for the new position!
It seems that I had better consider it. However, considering J in this simple calculation does not make things OK (such as fictitious stresses).
We all know that the Abaqus give cauchy stresses as a result in current space. It should be pointed that output stresses must be according to the input strain-hardening, but it is not True for near rigid plastic material. You can check it out.
In reply to Thank for your advice
Glad it was fixed. The use of the NLGEOM option has an important theoretical background, so you might want to ask your professor about that. One key part of that is the different strain measures used in linear vs. nonlinear analysis. What you saw is where if you rotate an element without stressing or straining it you will actually get nonzero strain output if you use the linear strain measure. If you use a nonlinear strain measure it will correctly output 0.
In reply to First, can you confirm that
Dear Marcus Rademacher,
Thanks to your advice, I found my mistake and corrected it. The problem is I set NLGEOM=off in abaqus Standard. When I run with NLGEOM=on, It work perfectly.
Again, thank you for your useful help.
regarding to my last post, You can check the abaqus stresses kind in plot result by simple tension example of a rod, if you check it correctly you will realize that abaqus shows cauchy stresses.
First apologize me for typing mistakes, all above stresses should be written in deviatoric parts. It was my first time to write equations in latex and html and it confused and distracted me a lot.
Thanks for your guide about trial stress and FEM application in large deformation plasticity, but I have written J2 large deformation plasticity code before, so please trust me ;-). The point is not the simplicity of yield condition, the point is that whether you have approximated the equivalent plastic strain correctly or not.
In your video you have written below equation to evaluate equivalent plastic strain:
then you have concluded that eps=66 . Actually you mean:
where K is the isotropic hardening parameter. Your formulation is not reasonable since it is for small deformation theory. You have ignored Jacobian of deformation gradient which is wrong, You should approximate the equivalent plastic strain from this formulation which is better approximation for large deformation theory:
In small deformation theory J or Jacobian is nearly equal to one so the effect of nonlinear geometry is not clear.
For checking the correctness of Yield condition that I wrote, please check Simo and Hughes 9.2.14 and 8.2.1.
First, can you confirm that you're running with NLGEOM=on? Are you using Standard or Explicit? Do the elements look like they're twice as long as they were?
In your field outputs, include "LE" which is the strain components. If those elements have 0 (or nearly 0) strain as measured with LE, then you're fine.
First of all, I want to thank you for your comment, but it's not reasonable. You just mentioned the simple relation of Mises plasticity theory. In computational plasticity, for computing the trial stresses and implementation, You can find clearer relation in detail (e.g. Simo and Hughes- Computational inelasticity).
Next, you must use it in FEM code to understand what is occurred in computation procedure.
It is worth to mention that the compatibility between stress and strain at This particular situation (Plane strain plasticity) in Abaqus is not True.
In reply to the problem was in a option
my abaqus simulation of time of flight diffraction technique not differentiating diaffracted wave and lateral wave.both gives same amplitude.what to do to gett a better result?.I am doing my work based on "shear wave TOFD by baskaran".any suggestion?
In reply to Dear aslan
Dear amin, I think I found why abaqus gives you strange results. Since you have turned on nlgeom in your solution then your plastic formulation is not the same as small deformation theory.
If we neglet the plastic spin then the yield stress condition can be stated as folllows for large deformation theory:
where is deviatoric part of symmetric mandel stress tensors and G_y_0 is initial yield stress and R is isotropic hardening parameter. for isotropic materials the above equation can be reduced to:
where is spatial kirchhof stress tensor and the bar on it shows rotated kirchhof stress. since rotation has no effect on above formulation we can rewrite:
and since the relation between Cauchy stress and Kirchhof stress is:
So it can be said:
where is Cauchy stress and J is jacobi of deformation gradient. The equivalent von Misses stress in abaqus is based on this formulation:
So the yield condition can be stated as follows:
The reason why you estimated unphysical large plastic strain is that you ignored J in your formulation.
In reply to Dear amin
As it is obviously shown in that simplest example, the reason is completely mathematical. We derived and developed continuum equations for plane strain plasticity and implemented in a Fortran code to resolve this fault.
For the Abaqus simulation, the implicit method was used. However, you can also decrease the time step, but you will never get the right results.
I'm not an expert in abaqus, but your example is interesting, as you mentioned in your video the the strain is not physical....
Is there any contour of equivalaent platic strain?
Was your solution implicit or explicit?
because large substep explicit gives wrong answeres.
In reply to initial void ratio for soil
you need to do it in a script file, CAE doesn't support this option very well
You would need to couple the nodes of two beams to the nodes of a master beam (likely the center one). That said, I'm not entirely sure this is a completely valid way to use beam elements. I think you'd be better off using solid elements or shells for this. That'll ensure you capture the transverse effects correctly.
Dear Prof Huang,
Thanks so much for sharing! I believe this type of papers are very helpful for young researchers in mechanics to understand and learn more about the most important resarch areas in the field. I look forward to reading more of these papers in JAM. Thanks!
In reply to Good news
Looking forward to reading more "Perspective paper"
Great to know JAM will include this type of paper. Looking forward to reading more "respective paper".
Such a type of paper will be very beneficial to readers and we are happy to see that JAM is becoming more and more influential.
Dear Yonggang, this is a great idea! Perspective paper is very important to both the academic society and the journal.