True vs engineering material curves

[shingouz]

Hi,
I'm trying to model a shear lap joint composed of 2 aluminium plates and a standard bolt to study its mechanical behavior under static loadings. I have engineering and true curves for aluminium material and until now i'm using engineering curves but I've seen that some researchers use true strain-stress curves. Is using engineering curves correct for my case?
Thank you in advance for help

 

[ESPcomposites]

It depends on the solver. Let me deviate for a second since many of us work with multiple analysis programs. MSC/NASTRAN uses either engineering or true stress/strain curves, depending on which solution algorithm is used (106 vs 600). The point is, it depends on what the solver is doing on its end. This would explain why you may have seen multiple approaches.

That said, most solvers (including ABAQUS) do use true stress/strain. But you should check the documentation to be sure. It is possible that for some reason this is not true (no pun intended).


Brian

http://www.espcomposites.com

 

[Drej]

The decision whether to use True or Engineering material curves depends on the level of strain you expect to see in the analysis and also on the 'non-linearity' of the stress/strain curve for the material, especially within the region of strain you are interested in.

True stress/strain and Engineering curves generally (for most structural materials) show a similar behaviour up to about 5% strain, at which point the True curve will differ (increase) owing to the necking area being accounted for. Therefore, if you expect to capture these strains accurately beyond this level you will need to use True stress/strain data. But as I say, you will also need to look at your material behaviour to confirm your choice. If there is little or no difference up to the level of strain you are seeing then using the Engineering stress/strain curve should be fine.


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