Energy balance relative in dynamic explicit calculation

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Hello everyone,

I’m new here and this is my first post.

I have a question regarding the value shown in the solver output under “energy balance relative”.

I’m trying to understand what this value represents. My assumption was that if I compute the ratio of energy increase to initial energy, I should get the same value, but that doesn’t seem to be the case.

Does anyone know what “energy balance relative” actually measures?

For context: I am using Calculix with PrePoMax, I am modelling an impact with the solver PASTIX with an explicit procedure.

Thank you in advance for your help and for making this site such a valuable source of information.

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It seems to be handled here in the source code: CalculiX/src/printenergy.c at 8b9081635cf95cb2b00ba7176bdc6ee75e0e9f89 · Dhondtguido/CalculiX · GitHub

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It is also explained in the ccx manual 2.23.

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Yeah, but that’s for implicit dynamics (so e.g. no energy for mass scaling).

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Thank you for your helpful answers.

The documentation confused me because it mentions the implicit context, so I was wondering if this value is relevant for the explicit procedure.

Now I understand why I don’t get the same result with a simple ratio of energy increase / initial energy. From what I’ve understood, CalculiX normalizes the energy balance using the Belytschko criterion.

In my interpretation, this normalization is useful when we expect an evolution of energy in the model, such as a mass accelerating under a force. In my case, I have a mass with an initial velocity followed by an impact. The kinetic energy is partially converted into internal energy, but the total energy should remain constant. Therefore, this normalization seems to have little relevance for my scenario.

Could you confirm if I understand this correctly?

Thank you again for your time.

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