how to block the rotations of loading plates?

Hi Behzad,

Your description sounds very strange to me. You described two consistent ways to define box bodies with constant, zero, angular velocites:
- the use of box() function with fixed = True
- or defining directly the blockedDOFs attribute of the bodies.

Usually (always, normally) YADE bodies with zero angular velocities do not rotate. Except if there is by chance some other funny Engine that will force them to do so (this depends on your complete simulation definition)...

So, I wonder what made you think these plates do rotate ??

Jerome,

well, that's my problem. They must stay fixed with zero rotation. but they don't. Check it out:

O.reset()
from yade import utils, plot
from yade import pack, qt

O.engines=[
ForceResetter(),
InsertionSortCollider([Bo1_Sphere_Aabb(),Bo1_Box_Aabb()]),
InteractionLoop(
[Ig2_Sphere_Sphere_ScGeom6D(),Ig2_Box_Sphere_ScGeom6D()],
[Ip2_CohFrictMat_CohFrictMat_CohFrictPhys(setCohesionNow=True, setCohesionOnNewContacts=True)],
[Law2_ScGeom6D_CohFrictPhys_CohesionMoment(),Law2_ScGeom_FrictPhys_CundallStrack()]),
NewtonIntegrator(damping=0.4,gravity=[0,0,0])
]

O.dt=1e-6
#============================MATERIALS===============================================================

cokeMat=O.materials.append(CohFrictMat(young=1e6,normalCohesion=1e3 ,shearCohesion=2e4 ,isCohesive=True, poisson=0.3,density=1377,frictionAngle=1,fragile=True,label='coke'))

cokeMat=O.materials.append(CohFrictMat(young=1e7,normalCohesion=1e6 ,shearCohesion=5e5 ,isCohesive=False, poisson=0.3,density=1377,frictionAngle=500,fragile=True,label='wall'))

#================================================================================================

sp=pack.SpherePack()
pred=pack.inCylinder((0,0,0.002),(0,0,0.21),0.05)

O.bodies.append(pack.regularOrtho(pred,radius=0.005,gap=-1e-6, material='coke'))

#============================WALLS===============================================================

box_lower = O.bodies.append(box((0,0,0.0),(0.05,0.05,0.0001),fixed=True,material='wall'))
box_upper = O.bodies.append(box((0,0,0.21),(0.05,0.05,0.0001),fixed=True,material='wall'))

O.bodies[box_upper].state.blockedDOFs='xyzXYZ'

O.bodies[box_lower].state.blockedDOFs='xyzXYZ'

#================================================================================================

for x in range(len(O.bodies)):
 if (O.bodies[x]):
                if isinstance(O.bodies[x].shape,Sphere):
   O.bodies[x].shape.color=(0,0.3,0.7)
  else:
   O.bodies[x].shape.color=(0.51,0.51,0.51)

O.engines=O.engines+[UniaxialStrainer(strainRate=-20,axis=2,asymmetry=0,posIds=[box_upper],negIds=[box_lower],
crossSectionArea=0.0025,label='strainer')]

I tried your script and could not see anything regarding plates rotation (for me they just move according to translation). So, I still wonder what made you think these plates do rotate ? ;-)

Sorry, depending on the yade version I use, I may observe some plate rotation O.iter ~ 30000. Keep in touch..

(I guess it's related with UniaxialStrainer which by the way is probably responsible for changing the blockedDOFs of your plates. Ask for this attribute after running your simulations, and you have now blockedDOF = 'z' instead of 'xyzXYZ')

Jerome,
As for #4 yes that's exactly what I have got.

And #5 is solving the problem. Actually, I was not aware that an engine like uniaxialStrainer can modify the DOFs.

Thanks for the complete answer.
Cheers,
Behzad

Thanks Jérôme Duriez, that solved my question.