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Hoping for a match.
Posted 24.05.2014, 03:47 GMT-4 Materials, Results & Visualization, Studies & Solvers, Structural Mechanics Version 4.3a 2 Replies
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Before starting simulating tensile tests on defective steel bars, I want to make sure that the software behaves properly : I define the behavior of my material by interpolating some points (true strain/true stress) of an experimental hardening function, then I run the software for a simple cylindric bar without defects.
The software should normally return a behavior curve similar to the one I submitted. Unfortunately, this is not the case. One can see the difference on the file attached (xlsx).
I took care to choose the best interpolated points that reproduce the experimental behavior curve as faithfully as possible, and I verified that my points are ok by plotting the interpolated hardening function on the software interface before running the computing. I also tried to change my points (choose more points at the end of the curve to insist on that part for instance) but the numerical behavior curve has always the same shape, the one shown on the attached file. I really don't understand why it does not behave properly through all the strain interval. May be it's the type of extrapolating that I selected (linear) ?
If you have any idea or comment, feel free to share it ;)
Regards.
Attachments:
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It looks like the necking of the bar occurs to early in your simulation. Are you using the "Large plastic strains' option? Also, please take a look at the model "Necking of an Elastoplastic Metal Bar" in the Model Library.
Regards,
Henrik
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When strains reach 20% like you have here it is important to use the “Large plastic strains” option as Henrick specified and you are probably getting necking. It is also important to know how stress and strain are defined. Most experimental data report engineering stress and engineering strain. When you select the large plastic strains option I believe COMSOL is expecting “true” stress and plastic strain. You should therefore convert your test data to these measures if necessary. The differences are insignificant at say 2% strain but at 20% they are not.
Nagi Elabbasi
Veryst Engineering