Energy balance in a quasi-static explicit analysis

[Dave442]

Hi all,

I would like to ask some advice on interpreting whether or not my quasi-static solution is acceptable. In the manual it says: "As a general rule the kinetic energy of the deforming material should not exceed a small fraction (typically 5% to 10%) of its internal energy throughout most of the process"

I have a model involving two parts which undergo large deformation and come in contact. At the end of the simulation I plot kinetic vs. internal energy for the model as a whole and for the individual parts. I can see that for the model as a whole and for one of the parts, kinetic energy is well below 5% internal energy throughout the analysis. However, for one of the parts in the analysis the kinetic energy exceeds 5% internal energy for a very short period of the (~2.5% of total time) and then quickly becomes negligible. If I animate the results of my model I can see this part undergoing a small oscillation as a result.

I was wondering how should these results be treated? Should I modify my analysis to reduce the kinetic energy in the problematic part? Or, as the period for which the kinetic energy exceeds 5% internal energy for the part in question is small compared to the overall solution time, are these results acceptable? Just curious to get other peoples opinions.

Thanks in advance,
Dave

 

[mechfeeney]

Pretty sure you're in the clear. The key part of the quote you gave is "throughout most of the process." Throughout most (97.5%) of the process you are below 5% and it's fine at steady state, so I think it's valid.

 

[Dave442]

Hi,

Thanks for the response. I guessed the results were probably valid considering the period of high kinetic energy is so short. Just needed a bit of reassurance!

Thanks again,
Dave