Calculating normElastEnergy

Hello,

it depends on material model [1,2,3]. In [2,3] cases the calculation is (in
python pseudocode):

##########################
ret = 0.0
for i in O.interactions:
  fn = i.phys.normalForce
  ret += fn.squaredNorm() / i.phys.kn
##########################

The only exception is the HertzMindlin law [1]
cheers
Jan

[1] https://github.com/yade/trunk/blob/master/pkg/dem/HertzMindlin.cpp#L118
[2]
https://github.com/yade/trunk/blob/master/pkg/dem/CohesiveFrictionalContactLaw.cpp#L23
[3]
https://github.com/yade/trunk/blob/master/pkg/dem/InelastCohFrictPM.cpp#L67

2015-11-28 5:17 GMT+01:00 ipemath <email address hidden>:

> New question #275834 on Yade:
> https://answers.launchpad.net/yade/+question/275834
>
> How normElastEnergy is calculated in Yade. Please provide some reference
> for this calculation?
>
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Sir,

Thanks for the reply. Sir I am giving my coefficient of restitutions equal to 1.0. According to my engineering mechanics teacher, then the bodies are supposed to behave a rigid. Then how can there be normal Elastic energy. They are supposed to be zero isnt?

 I wanted to learn the kinetic energy propagation down a granular bed. There I found gross imbalance in energy while not taking normElastEnergy(), thats why this issue came up in the first place. Please help

Hello,

> Thanks for the reply. Sir I am giving my coefficient of restitutions
> equal to 1.0. According to my engineering mechanics teacher, then the
> bodies are supposed to behave a rigid. Then how can there be normal
> Elastic energy. They are supposed to be zero isnt?
>

the body is considered rigid, but the interactions between them. During the
contact, some kinetic energy of particles is transformed into potential
energy of elastic deformation if the interaction.Coefficient of restitution
equal to 1 means, that **after** the contact, the energy is preserved
(there is no dissipation).

To have really no dissipation, also make sure you explicitly set damping=0
to NewtonIntegrator and you use sufficiently small time step.

>
> I wanted to learn the kinetic energy propagation down a granular bed.
> There I found gross imbalance in energy while not taking
> normElastEnergy(), thats why this issue came up in the first place.
>

yes, if you only investigate kinetic energy, it is not constant.

cheers
Jan

PS: also read [1], next time please give more information (basics is
enough, e.g. what material model you use etc.)
[1] https://yade-dem.org/wiki/Howtoask