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[Selma <question248246@xxxxxxxxxxxxxxxxxxxxx>]

New question #248246 on Yade:
https://answers.launchpad.net/yade/+question/248246

Hi,

I am trying to detect interaction forces when depositing an object of conical shape into the soil. 
For that purpose I use gravel material for soil and steel for object which is made out of facets. These are the parameters I set up for soil and object, respectively:

gravel = O.materials.append(FrictMat(density=1602,young=120e6,poisson=.25,frictionAngle=.61))
stainless_steel = O.materials.append(FrictMat(density=7740,young=180e9,poisson=.305,frictionAngle=.79))
This is how I set up engines:

O.engines=[      
   ForceResetter(),
   InsertionSortCollider([Bo1_Sphere_Aabb(),Bo1_Facet_Aabb()]),
   InteractionLoop(	
      [Ig2_Sphere_Sphere_ScGeom(),Ig2_Facet_Sphere_ScGeom()], # handle sphere+sphere and facet+sphere collisions
      [Ip2_FrictMat_FrictMat_FrictPhys(frictAngle=None)],
      [Law2_L3Geom_FrictPhys_ElPerfPl()]
   ),
   NewtonIntegrator(gravity=(0,0,-9.81),damping=.3),
]
# set up time step
O.dt=.5*utils.PWaveTimeStep()

As for moving the object I use PyRunner and in every time step I change its position.

When I try to move the object while in soil (with the aim of finding trajectory with which minimum force would be exerted), the soil becomes unstable, and particles move outside of the bounding box. Everything is ok if the deposition is made as a straight line without any additional movements. 
I would like to know why does this happen and how can it be fixed? Is it due to high density of the object, high young modulus? What particular effect has velocity of the object?
I would be very grateful for any further advices on this matter, since I am new to Yade and the matter of soil behaviour and soil models in general. 

Thank you,

Selma


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