Hi,
I did an quasi static analyse. As a result of my analysis, total energy of the output set (etotal) is everytime negative and after some steps etotal increases exponentially in negative area. In other words, My external works is higher than strain energy of the whole model.
The artificial energy is really small compared to strain energy of the whole model. I couldnt understand the reason. If you could help me that would be great
Best Regards...
The energy balance using the total energetic quantities computed bu Abaqus (as history output) is given by the following the equation :
- Etotal = ALLIE + ALLKE + AllVD + AllFD - ALLWK=constant.
the question is , why Etotal = constant ? it should be zero, in other words, all
the external work done should be transfomed to other forms of energy like internal energy and kinetic enery and so on. and ths is an energy balnce.
Therefore, Etotal should be zero. if i am wrong, please correct me.
In my model i find that Etotal is always negative. i want to know is there any thing wrong in my model.
Hi Adriana, in my simulation in some steps go unstable and then Abaqus add some damping. Therefore Etotal goes in negative situation. You could have similar situation also. If your E total looks really constant when comparing with internal energy. I think that is okay.
Hi,
if you look at the "Getting started with Abaqus" manual, it explains the various energy measures. Etotal should be constant, not necessarily 0. Checking the Etotal is a good way to evaluate if your model is "leaking" energy = poor setup. If you can't figure out what goes wrong, maybe try to output element energy measures and see if you can spot which element(s) cause the exponential increase.
Also it's worth noting, that some features such as viscoelastic damping do cause "leak", but these are clearly marked in the manual. For the most common applications, your Etotal should be very close to constant.
Hope this helps,
Best regards,
David
Hi,
I have the same problem when I was computing 4 point bending problem, the ratio of ETOTAL/External work is around 10%. I found out that if you are using contact algarithom and mass scaling method, you are more likely to obtain negative ETOTAL.
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