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[Chiara Modenese <question201769@xxxxxxxxxxxxxxxxxxxxx>]

Question #201769 on Yade changed:
https://answers.launchpad.net/yade/+question/201769

Chiara Modenese proposed the following answer:
Hi Anna,

Are you aware that you input in the model some rolling resistance (if
you try with the bool includeMoment=False you will see what I mean)? I
think that explains the behaviour. Can you please try to explain here
the purpose of your test? It may help us to give you a better answer.

Thank you,
Chiara

On 29 Jun 2012, at 07:01, anna effeindzourou wrote:

> New question #201769 on Yade:
> https://answers.launchpad.net/yade/+question/201769
> 
> Hi all,
> I am using the Hertz Mindlin contact law with a simple example a sphere rolling on a inclined facet and then on a horizontal facet. I've observed that the sphere is rolling up  and down.
> Here is a small script to help you understand the phenomenon.
> 
> 
> #!/usr/bin/python
> # -*- coding: utf-8 -*-
> from yade import utils
> 
> h=0.2
> 
> O.materials.append(FrictMat(young=1.7e8,poisson=0.20588,frictionAngle=radians(17),density=2650))
> s1=O.bodies.append( utils.sphere([0.0000001,0.5,h+0.1],.1,color=[0,1,0],fixed=False,wire=True))
> 
> 
> v1=(0,0,h)
> v6=(0,1,h)
> v2=(.5,0,0)
> v3=(2,0,0)
> 
> v4=(2,1,0)
> v5=(0.5,1,0)
> 
> f1=O.bodies.append( utils.facet([v1,v2,v5], dynamic=None, fixed=True, wire=True, color=None, highlight=False, noBound=False, mask=1))
> f2=O.bodies.append( utils.facet([v1,v5,v6], dynamic=None, fixed=True, wire=True, color=None, highlight=False, noBound=False,  mask=1))  
> f3=O.bodies.append( utils.facet([v2,v3,v4], dynamic=None, fixed=True, wire=True, color=None, highlight=False, noBound=False, mask=1))
> f4=O.bodies.append( utils.facet([v2,v4,v5], dynamic=None, fixed=True, wire=True, color=None, highlight=False, noBound=False,  mask=1))
> 
> ## time step
> O.dt=1e-5
> 
> O.engines=[
> 	ForceResetter(),
> 	InsertionSortCollider([Bo1_Sphere_Aabb(),Bo1_Facet_Aabb()]), 
> 	InteractionLoop(
> 	[Ig2_Facet_Sphere_ScGeom(),Ig2_Sphere_Sphere_ScGeom()],
> 	[
> 	Ip2_FrictMat_FrictMat_MindlinPhys(en=0.1, krot=1,eta=1)
> 	],
> 	[Law2_ScGeom_MindlinPhys_Mindlin(includeMoment=True),
> 	]),
> 	NewtonIntegrator(damping=0,gravity=(0,0,-9.81)),
> ]
> 
> Any ideas?
> 
> cheers, 
> Anna
> 
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