I'm currently doing the simulation of a tensile test in COMSOL for my Master thesis. The idea is to compare those results with the results I'll get from the laboratory doing a real tensile test. I'm currently having problems on how to plot the curves i described before. If someone could help would be very much appreciated.
René Christensen Can you also provide a Nastran file of your Comsol model?
Hi Nils Wagner I am sorry, but I don't have Nastran. I imagine it is not very difficult to replicate, I just fix one end of a geometry and apply a force in a static analysis. Post-process can give you any type of stress and strain, and a value for the displacement vs applied force. Perhaps if José Pierobon uploads his file so far more details will be revealed :-)
The tensile test measures force and the elongation over a distance, with an extensometer. That is not the same thing as plotting the s-e curve for a node (in the neck) in your FE model, so just be aware so you compare engineering or true stress and strain.
Hi René Christensen
As far as I know, Comsol is able to export models in NASTRAN format.
https://www.comsol.com/fileformats
Kenth Nilsson Thanks Kenth, don't know the method too well. It is always difficult to know how much the person asking knows, so often some starting point is needed to get the discussion going. You can do the displacement in steps as a parametric sweep for example, and evaluate reaction forces, which is probably closer to the test. But I only have so much time... :-) Perhaps only the plotting is issue, perhaps it is about getting started in the software, perhaps much more complex.
Hi René Christensen thanks for your reply. In your model i saw you made the Force-Displacement diagram based on one single point at the end of one of the faces of the body (Point 6).
Why using that point and not another? Would this diagram replicate the one made on a tensile test machine?
The tensile probe i'm using for my simulations is made of PLA and has different infill patterns to test the changes on the mechanical response. These probes will be further 3D printed and replicate the test in the lab.
Here there is an example of the Stres vs Strain diagram i got from simulating a simple probe, i coudn't upload the honeycomb one since the file was too heavy.
Hi Nils Wagner , sorry i also don't have Nastran, hope the file i uploaded is useful for you :)
Hi Kenth Nilsson thanks for your reply, i noticed the same thing. I added a parametric swept as René Christensen suggested on my simulation and I used a force ranging from 0 to 100 kN and plot the Stress and Strain curve for a node in the middle of the specimen, which I think could simulate the measurements of the extensometer.
Hi Nils Wagner i exported my model in Nastran format, i hope it's useful for you :)
Hi José Pierobon ,
Thank you very much for sharing the Nastran model. The geometry is pretty simple. IMHO, a structured mesh would be better. Material properties, boundary and loading conditions are missing. Can you also provide that information?
A picture of a structured mesh is attached.
Hi Nils Wagner ,
Thank you for your reply. The actual geometry of the probe is rectangular and has a honeycomb infill, the file for this geometry in Nastran format is also attached :)
The material is PLA, a thermoplastic 3D printing material
E = 3,5 GPa
Poisson's ratio = 0,3
Density = 1240 kg/m3
The boundary conditions for a tensil test are a fixed boundary on one of the faces and on the opposite one a boundary load that ranges from 0 to 15kN.
Kind regards.
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