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[Chiara Modenese <question256283@xxxxxxxxxxxxxxxxxxxxx>]

Question #256283 on Yade changed:
https://answers.launchpad.net/yade/+question/256283

Chiara Modenese proposed the following answer:
Just to say that the HM contact model has been widely tested for
sphere-sphere contacts but not with other elements. I am not familiar with
the formulation of facets but maybe somebody who is might be able to help
you?

Cheers,
Chiara

On 28 October 2014 16:46, Chareyre <question256283@xxxxxxxxxxxxxxxxxxxxx>
wrote:

> Question #256283 on Yade changed:
> https://answers.launchpad.net/yade/+question/256283
>
>     Status: Open => Answered
>
> Chareyre proposed the following answer:
> Hi,
>
> On 28/10/14 08:16, Alexander Smith wrote:
> > I tested the Hertz Mindlin contact model and noticed that shear and
> normal viscous damping is not accounted for in a sphere-facet contact. It
> behaves correctly with a sphere-sphere contact. I have attached a simple
> script below to illustrate my point. I just wanted to check before I report
> a bug.
> To me it sounds like a bug, but maybe it is intentional. Devs of the
> viscous model will tell.
>
> > Also, I noticed that a facet is made of two "triangles" and at the
> junction of the two it appears the sphere is in contact with both surfaces.
> This increases the normal force and effects shear force and contact moments
> (shown by setting a=0 in the script below). Is this correct?
> No, it is not correct. It is a known issue of facet-sphere contacts, and
> it is more or less solutionless in the context of facets as they are now.
> Thus, I would not recommend to try and fix this by yourself.
> Some solutions are being implemented and should be released soon. They
> replace facets by more advanced shapes.
>
> > I am developing a contact model and  I need some guidance on how to fix
> it to ensure that the contact model behaves correctly on flat surfaces.
> If the surface is flat, then it can be a single facet, or a a box.
> Problem solved (or?).
>
> Bruno
>
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