Explicit simulation energies do not add up to ETOTAL

[bennytehcat]

I'm having an issue running an explicit simulation and hope someone can shed some light on this.

According to abaqus documentation (

http://www.egr.msu.edu/software/aba...usb/default.htm?startat=pt03ch06s03at07.html,

near the bottom of page), the Total energy balance for an explicit simulation is:

ETOTAL = ALLIE+ALLKE+ALLVD+ALLFD-ALLWK

When I run my simulation and look at these terms, there is a significant energy loss during loading. I attached a plot direct from abaqus showing the above energy terms for the *whole model*. ALLFD, ALLVD, and ALLWK are zero, meaning the only energy in my system should be Kinetic and Internal. The plots however show that the internal energy accumulation (whole model) is not equal to the kinetic energy loss (whole model). Where could this energy be going? It appears to only be during the transient that it loses energy.

Abaqus Plot showing 6 energy terms:

Any help is greatly appreciated.

 

[skywalker90]

Hey bennytehcat,

I am also doing an explicit analysis with Abaqus in the moment and I have the same problem as you. When I apply the energy balance equation of the manual my energies do not sum up to ETOTAL. ETOTAL is bigger than my calculation results in all simulations so far. I will deal with it in the coming week and I will let you know when I find the reason for it. Do you already found out why it is like this?

Kind regards,

skywalker

 

[kelvinlym]

Hi,

Did you have Mass scaling on?

This could lead to artificially high mass scaling which may increase the KE of your model.

 

[skywalker90]

Hi,

I found the reason for it. I forgot the internal work by penalty contact (ALLPW). With this energy the summation is correct. Nevertheless ETOTAL is not constant in the beginning of the simulation due to ALLPW. Does this mean that I have an error in my model? I read that ETOTAL must always be constant...

I have mass scaling on but the energy due to this is zero in my simulation