Stress-strain curve - Inability to find the same behavior by performing simulations

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1

Hello

I am a student and I work on the simulation of tensile tests on SolidWorks to anticipate the behavior of new composite materials. My primary objective is to find the same results between tensile tests that have been carried out in the laboratory and tests that I will carry out on SolidWorks.

I carry out these tests on a simple bar:

Unfortunately I don't find the same results when going through SolidWorks. Thinking this was the data I was entering for my material, I used one from the SolidWorks library.

After many tests, I don't understand why I can't find exactly the same stress-strain curve that entered into the characteristics of the material.

 

I'm working on SolidWorks 2017. I perform non-linear, 2D simulations. I have already done a convergence study for the mesh, which should be good. To find my strain curve after simulation, I run simulations for different forces for which I recover stress, strain and displacement and I draw these curves myself.

Here are the differences I can find between the curve given in the properties of the materials (in orange) and the stress strain curve in blue following the simulation.

Do you know where these differences in stress and strain can come from?

I also have this error message for the larger forces:

In my case, do I have it when my model breaks?

In what situation should we choose the options of long journeys and great constraints?

Thank you very much for your answers

Aurélie

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Hello Miss Aurélie

Just by reading your text, several things catch my attention.

1°) you say New composite materials or Solidworks is not a very suitable software for composites, especially if they are multilayer 2D or 3D composite as found in aviation in particular.

2° ) You use the ugly word  :-)  which would be "rupture" when you say "when my model breaks".

Indeed, I frequently say it on this forum, PEF simulation software, including SolidWorks, only works in the elastic field and never in the plastic field. Only the plastic field would make it possible to account for the breaking point. However, no software deals with shortages.

The purpose of the PEF simulation is to indicate that beyond a certain point - usually given by the Von Mises - it is terra incognita: which means in ordinary language that beyond this point it can fart at any time without being able to say that it is 1 mm further or 9.75 cm further and 200 kg or 2 tons more. This is why, in addition to the Von Mises, the calculation of the safety factor is added, which gives crucial information on the meaning of the elastic limit. To put it another way, with margin and under margin.

To solve your problem, you would have to look at CATIA which has specialized software for composites, but there too it will remain AMHA in the elastic field, not in the plastic field. Maybe on the multiphysics side, but I don't know much about them.

3°) it is likely when you have an error in your simulation parameters, either at the level of contacts and/or long trips that are not selected as such. Because the system seems to go bananas from the first iteration (first step), which may mean that you may not have chosen the right solver either.

You would have to review all of your parameters, but in relation to the goal you are pursuing, it probably does not make sense in the light of my opening remarks.

Kind regards

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3

Hello

Thank you for your answers.

We were aware that SolidWorks was not the best software to carry out this kind of simulation. Unfortunately we don't have any other options at the moment and we think we can already have some answers before confirming them on another software.

On the other hand, I did not know about the existence of the safety factor which will be very useful to me.

Indeed, I had made some configuration errors, I now find much more consistent results.

Good luck!

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Good evening Aurélie

You can close the topic if you're happy with the answer.

Kind regards