ViscElMat : about restitution coefficient.

Hi Francois,

it seems, you are right. If we do it, we need to recalculate tc according
to (19). Not sure, how to do it better. One proposal is to have a variable,
something like tcUpdated, in ViscElPhys where we will store the updated
tc value.

Best regards

Anton

2014-09-10 16:39 GMT+02:00 Kneib François
<email address hidden>:
> New question #254308 on Yade:
> https://answers.launchpad.net/yade/+question/254308
>
> Hi Anton,
>
> you recently changed the visco-elastic law to avoid any attractive force according to Schwager 2007. As a consequence the effective contact duration and restitution coefficient are not respected relative to the one you set into the material. In other terms, the equations in Pournin 2001 are no longer rightful.
>
> What is your position about this issue ? Do you think that we should implement the equation that Schwager propose (eq. 19) ? (but this equation seems much more difficult to implement than Pournin's one).
>
> Thanks.
>
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Hi Anton,

We thought about this with Raphaël Maurin, and it seems that there is no
analytic solution to find Tc and Cn from En. So, to our knowledge, we need
an iterative algorithm of "zero finding". It would be not so time-consuming
and give acceptable solution within 10 iterations as the function is very
simple (graph fig. 2 in Schwager 2007). We found also that Schwager has
forgotten a minus in the second equation of (21). I will work on it and
propose a code on monday, unless you have a better solution.
Your question #254308 on Yade changed:
https://answers.launchpad.net/yade/+question/254308

    Status: Open => Answered

Anton Gladky proposed the following answer:
Hi Francois,

it seems, you are right. If we do it, we need to recalculate tc according
to (19). Not sure, how to do it better. One proposal is to have a variable,
something like tcUpdated, in ViscElPhys where we will store the updated
tc value.

Best regards

Anton

2014-09-10 16:39 GMT+02:00 Kneib François
<email address hidden>:
> New question #254308 on Yade:
> https://answers.launchpad.net/yade/+question/254308
>
> Hi Anton,
>
> you recently changed the visco-elastic law to avoid any attractive force
according to Schwager 2007. As a consequence the effective contact
duration and restitution coefficient are not respected relative to the one
you set into the material. In other terms, the equations in Pournin 2001
are no longer rightful.
>
> What is your position about this issue ? Do you think that we should
implement the equation that Schwager propose (eq. 19) ? (but this equation
seems much more difficult to implement than Pournin's one).
>
> Thanks.
>
> --
> You received this question notification because you are a member of
> yade-users, which is an answer contact for Yade.
>
> _______________________________________________
> Mailing list: https://launchpad.net/~yade-users
> Post to : <email address hidden>
> Unsubscribe : https://launchpad.net/~yade-users
> More help : https://help.launchpad.net/ListHelp

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