Finding the stress or strain on each individual node? 1

[tmillar]

I have just submitted a model for analysis and got the results odb. I was just wondering is it possible for the analysis to tell me the exact stress or strain of an exact node on a model?

 

[mechfeeney]

Yes. Tools --> Query --> Visualization Module Queries (Probe Values)
A 'Probe Values' window will pop up. Click 'Field Output' and change to the appropriate stress variable you want. Select Nodes instead of the default 'Elements' under Probe: [Elements]

 

[tmillar]

Thanks a lot feeney!

 

[mechfeeney]

No problem and good luck!

 

[tmillar]

Maybe I could pose another question to you mechfeeney?

Do you know if this is the correct formula to find strain energy density?


strain_energy_density = 0.5*von_mises*max_principal_strain

Where:
von mises has the field output "S"
max principal strain has the field output "E"

 

[mechfeeney]

Hi Tmillar,

Stress and Strain are output variables that come default with a static simulation in Abaqus. You are requesting a variable that is not part of this so called 'default' config. To output strain energy density you need to do a minor tweak to your initial simulation setup BEFORE you run the job. Now if you look in the Model Tree, you will see the name of your model. Expand that out and go to Field Output Requests (below Assembly and Steps). Double click on that and setup a new field output request. The first window that pops up ask you to name it and select the Step. Use the step that defines your static loading (defualt Step 1). Next observe the list of output variables available. Find Energy. You can click on the entire energy category or you can expand it out and get exactly what you need. For your needs, all you have to select is ELEDEN, All energy density components. Next step is running the job again. Then do the probing technique I previously discussed. You will find a bunch of differnt energy density outputs. My guess is that you are doing an elastic static case, so you would select ESEDEN, which stands for Total elastic strain energy density in the element for whole element.

 

[mechfeeney]

I realized I didn't actually answer your question. The equation that you have

strain_energy_density = 0.5*von_mises*max_principal_strain

is, as far as I know, correct.

 

[tmillar]

Thanks alot mechfeeny, I really appreciate your help. So I did it both methods and got the following results for 16 different nodes:


Node ID E S Strain Energy Density ESEDEN

1 4.24E-05 -17.9436 -3.81E-04 4.18E-03
2 3.91E-06 5.16E-01 1.01E-06 1.65E-06
3 5.18E-06 8.41E-01 2.18E-06 1.65E-06
4 4.95E-05 11.4112 2.83E-04 1.71E-04
5 2.95E-05 5.70879 8.43E-05 1.08E-04
6 7.16E-05 16.3744 5.86E-04 2.42E-04
7 4.01E-05 7.50915 1.51E-04 2.34E-04
8 2.63E-04 67.3872 8.87E-03 4.22E-03
289 4.24E-05 -17.9436 -3.81E-04 4.18E-03
290 3.91E-06 5.16E-01 1.01E-06 1.65E-06
291 5.18E-06 8.41E-01 2.18E-06 1.65E-06
292 4.95E-05 11.4112 2.83E-04 1.71E-04
293 2.95E-05 5.70879 8.43E-05 1.08E-04
294 7.16E-05 16.3744 5.86E-04 2.42E-04
295 4.01E-05 7.50915 1.51E-04 2.34E-04
296 2.63E-04 67.3872 8.87E-03 4.22E-03

If ESEDEN and strain energy density (calculated by 0.5*S*E) are supposed to be the same, they are not giving the same answer

 

[mechfeeney]

In most cases you're off by an order of magnitude. Hmmmmmm....Well ESEDEN is an elemental variable, not a nodal one. Are you probing elements for your hand calc version? Try probing the elemental stress and strain for the hand calc and compare with ESEDEN.

 

[mechfeeney]

This has me a bit stumped. There is another ouput variable called SENER (Strain Energy Density at integration points). I can't find much information about the mathematics behind how Abaqus calculates SENER or ESEDEN.

 

[tmillar]

Hello mechfeeney,

SENER is the correct output variable that I should be using, the only thing problem is that it is at the integration points and I wish it to be at the nodal points. I am not sure how I would get this to work? Perhaps when setting up the analysis? Creating another step file?

Also do you know how I could find the area of each of the elements? Is there an easy way to do this?

Regards