How to apply a constant force value

Hi Felipe,

I had found some issues

next time please be more specific, this information gives no help.. Does
the body disappear? Yuo prescribe force and it does not move?....

apply a force value on the surface that is moving at constant velocity

Either you apply force and the result is positions/velocity, or you
prescribe velocity and the result is force. It is not possible to prescribe
both force and velocity...

1 – A surface which was created by O.bodies.append([leftBox,
> lowBox,rightBox,upBox,behindBox,inFrontBox])

to prescribe force you have two options:
#############################################
O.forces.addF(upBox.id) # [1] for just one iteration
O.forces.setPermF(upBox.id,someForceVector) # [2] sets permanent force
# probably you will also have to set mass and dynamic flag to the body:
upBox.dynamic = True # [4]
upBox.state.mass = someMassValue
upBox.state.inertia = someVector # you can check what is the value of mass
and inertia, it might be 0 or NaN causing the bodies "disappear"
# upBox.state.blockedDOFs = ??? # to block some DOFs like rotations etc.
#############################################

to prescribe velocity:
#############################################
upBox.state.blockedDOFs = 'xyzXYZ' # [3]
upBox.state.vel = someVelocityVector
#############################################

2- A geometry which was imported by rod1 = O.bodies.append(ymport.stl(
> mesh1+'.stl',wire=True,material='caixasup'))

the same approach as above, just you will have to identify the bodies you
want to adjust:
#############################################
upBox = O.bodies[someID]
#############################################

cheers
Jan

[1]
https://yade-dem.org/doc/yade.wrapper.html#yade.wrapper.ForceContainer.addF
[2]
https://yade-dem.org/doc/yade.wrapper.html#yade.wrapper.ForceContainer.setPermF
[3]
https://yade-dem.org/doc/yade.wrapper.html#yade.wrapper.State.blockedDOFs
[4] https://yade-dem.org/doc/yade.wrapper.html#yade.wrapper.Body.dynamic

Hello Jan,

thanks for all comments that you provided me.

By the way, i did not get to apply your solution on my program. Maybe, I am putting some incorrect values. Due to this information, i would like to ask to you how can i define the values to:

upBox = O.bodies[540]

O.forces.addF(upBox.id)
O.forces.setPermF(upBox.id,(0,10,0))
upBox.dynamic = True # [4]
upBox.state.mass = 10
upBox.state.inertia =(0,1,0)

is it correct?

#---- Def of the Imported Bodies ----#
rod1 = O.bodies.append(ymport.stl(mesh1+'.stl',wire=True,material='caixasup'))
rod2 = O.bodies.append(ymport.stl(mesh2+'.stl',wire=False,material='caixainf'))

#---- Def of the Plan ----#
upBox = box( center=(0,255,-25), extents=(50,1,50) ,fixed=True,wire=False)

O.bodies.append([upBox])

#---- Def of the Particles ----#
sp=pack.SpherePack()
sp.makeCloud((-35,-45,-35),(35,250,35),rMean=5,periodic=False,porosity=0.8,distributeMass=False,seed=0)
sp.toSimulation()

#---- Def of the Engines ----#
O.engines=[
 ForceResetter(),
 InsertionSortCollider([Bo1_Sphere_Aabb(),Bo1_Facet_Aabb(),Bo1_Box_Aabb()]),
 InteractionLoop(
  [Ig2_Sphere_Sphere_ScGeom6D(),Ig2_Box_Sphere_ScGeom6D(),Ig2_Facet_Sphere_ScGeom6D()],
  [Ip2_FrictMat_FrictMat_FrictPhys()],
  [Law2_ScGeom_FrictPhys_CundallStrack()]
 ),
 NewtonIntegrator(damping=0.7, gravity=[0,-9.81,0]),
 GlobalStiffnessTimeStepper(active=1,timeStepUpdateInterval=100,timestepSafetyCoefficient=0.8),
 ]

#---- Def of the Force ----#
upBox = O.bodies[540]

O.forces.addF(upBox.id)
O.forces.setPermF(upBox.id,(0,10,0))
upBox.dynamic = True # [4]
upBox.state.mass = 10
upBox.state.inertia =(0,1,0)

#---- Def of the Plots ----#
from yade import plot
qt.Controller()

O.run(3000,True)
qt.View()
O.run(3000)

Thanks Jan Stránský, that solved my question.