yade-users team mailing list archive

[Chiara Modenese <c.modenese@xxxxxxxxx>]

Dear Christian,

viscous damping is already implemented in the current version of
HertzMindlin contact law. Damping can be applied in both normal and shear
directions. Actually, in the code you can choose between two different forms
of damping:
1) the first one refers to the solution of a damped linear spring-mass
system where damping coefficient is a fraction of the critical damping
coefficient for the system. The current contact stiffness is employed in
such a case (since the law is non-linear, a tangential contact stiffness can
be computed each time step).
2) the second one is based on a numerical solution provided by Tsuji et al.
(1992) which can be used to relate damping coefficient and coefficient of
restitution when non-linear spring is involved.

Up to you which method to choose, though to me the second option gives a
better physical interpretation of the phenomena.

The script in .../yade/scripts/Damping_HM.py should provide you a basic
example to start with. Let me know if you need further help with that.

 Chiara




On 29 June 2011 09:14, Christian Jakob <jakob@xxxxxxxxxxxxxxxxxxx> wrote:

> Hello again,
>
> I need to create a material with Hertz-Mindlin contact model (given
> shear modulus and poisson ratio) with viscous damping in normal and
> shear direction. The question is: How can I do this?
>
> I can create a viscous elastic material with linear contact model ...
>
> O.materials.append(ViscElMat(density=2700,kn=1e8,ks=1e8,frictionAngle=1,cn=0.002,cs=0.001))
>
> and I can create an inelastic material with Hertz model, but without
> viscous damping ....
>
> O.materials.append(NormalInelasticMat(young=2e7,poisson=0.3,frictionAngle=1,coeff_dech=1))
>
> if I try to combine, an error occured:
>
> O.materials.append(NormalInelasticMat(young=2e7,poisson=0.3,frictionAngle=1,coeff_dech=1,cn=0.002,cs=0.001))
>
> "AttributeError: No such attribute: cn"
>
>
> Regards,
>
> Christian Jakob
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