New question #707278 on Yade:
https://answers.launchpad.net/yade/+question/707278
Hi! I am trying to model a cylindrical triaxial test based on Pfacet and
ServoPIDController. I would like to model a triaxial compression test with
confining pressure equal to 50kPa. The bottom and top loading plates are
created using the 'facet' element. The top one is assumed to move slowly in the
vertical direction while the bottom one is fixed. The cylindrical walls are
generated using 'Pfacet' elements. Referring to [1], I wrote the current MWE
but don't know how to use the ServoPIDController to achieve servo control of
the flexible membrane with confining pressure.
The MWE is presented below:
from __future__ import print_function
from yade import pack, ymport, qt
import gts, os.path, locale, plot, random
import numpy as np
from yade.gridpfacet import *
import math
locale.setlocale(
locale.LC_ALL, 'en_US.UTF-8'
) #gts is locale-dependend. If, for example, german locale is used,
gts.read()-function does not import floats normally
############################################
### 1 ###
### DEFINING VARIABLES AND MATERIALS ###
############################################
# The following lines are used parameter definitions
readParamsFromTable(
# material parameters
young_w = 5e9, # Young's modulus of plates and walls
young_g = 1.8e6, # Young's modulus of grains [1]
den_w = 7874, # density of plates and walls
den_g = 980, # density of grains
poi_w = 0.3, # possion's ratio of plates and walls
poi_g = 0.25, # possion's ratio of grains
friAngle_w = 0.5,#radians(15), # friction angle of plates and walls
friAngle_g = 0.5,#radians(29), # friction angle of grains
# Parameters of cylindrical walls
x_cyl = 0.0547, # x-coordinate of center of cylindrical walls
y_cyl = 0.0535, # y-coordinate of center of cylindrical walls
z_cyl = 0, # z-coordinate of center of cylindrical walls
r_cyl = 0.0358, # radius of the cylinder
h_cyl = 0.14, # height of the cylinder
)
from yade.params.table import *
# create materials for spheres and walls
wallMat = O.materials.append(FrictMat(young = young_w, poisson = poi_w,
frictionAngle = friAngle_w, density = den_w, label = 'walls'))
sphereMat = O.materials.append(FrictMat(young = young_g, poisson = poi_g,
frictionAngle = friAngle_g, density = den_g, label = 'spheres'))
###############################################
### 2 ###
### IMPORTING GRAINS AND CREATING CLUMPS ###
###############################################
# spheres
pred = pack.inCylinder((x_cyl, y_cyl, z_cyl), (x_cyl, y_cyl, h_cyl), r_cyl)
sp = SpherePack()
sp = pack.randomDensePack(pred, spheresInCell=2000, radius=0.005,
returnSpherePack=True)
spheres = sp.toSimulation(color=(0, 1, 1), material=sphereMat)
# assign unique color for each sphere
currentSphereId = O.bodies[0].id
color = randomColor()
for b in O.bodies:
if b.id != currentSphereId:#change color each time clumpId changes
currentSphereId = b.id
color = randomColor()
if isinstance(b.shape,Sphere):#colorize spheres
b.shape.color = color
# create top and bottom plates
h_cyl = max([b.state.pos[2] + b.shape.radius for b in O.bodies if
isinstance(b.shape, Sphere)])
top_plate =
O.bodies.append(yade.geom.facetCylinder((x_cyl,y_cyl,h_cyl),radius=r_cyl*1.2,material=wallMat,height=0,segmentsNumber=10,color=(1,1,1),wire=True))
bottom_plate =
O.bodies.append(yade.geom.facetCylinder((x_cyl,y_cyl,0),radius=r_cyl*1.2,material=wallMat,height=0,segmentsNumber=40,color=(1,1,1)))
#O.bodies[top_plate].state.vel = (0, 0, -0.01)
#O.bodies[bottom_plate].state.vel = (0, 0, 0)
#O.bodies[bottom_plate].state.blockedDOFs = 'xyzXYZ'
# Define engine
O.engines = [
ForceResetter(),
InsertionSortCollider([Bo1_Sphere_Aabb(),
Bo1_PFacet_Aabb(),
Bo1_Facet_Aabb()],
sortThenCollide=True),
InteractionLoop(
[
Ig2_GridNode_GridNode_GridNodeGeom6D(),
Ig2_GridConnection_GridConnection_GridCoGridCoGeom(),
Ig2_Sphere_Sphere_ScGeom6D(),
Ig2_Sphere_PFacet_ScGridCoGeom(),
Ig2_Facet_Sphere_ScGeom(),
],
[
Ip2_CohFrictMat_CohFrictMat_CohFrictPhys(setCohesionNow=True,setCohesionOnNewContacts=True),
Ip2_FrictMat_FrictMat_FrictPhys()
],
[
Law2_ScGeom6D_CohFrictPhys_CohesionMoment(),
Law2_ScGeom_FrictPhys_CundallStrack(),
Law2_ScGridCoGeom_FrictPhys_CundallStrack(),
Law2_GridCoGridCoGeom_FrictPhys_CundallStrack(),
]
),
NewtonIntegrator(gravity=(0,-9.81,0),damping=0.1,label='newton'),
TranslationEngine(translationAxis=[0, 0, 1], velocity=-2,
ids=top_plate, dead=False, label='translat'),
CombinedKinematicEngine(ids=top_plate, label='combEngine', dead=True) +
ServoPIDController(axis=[0, 0, 1], maxVelocity=2, iterPeriod=100,
ids=top_plate, target=1.0e7, kP=1.0, kI=1.0, kD=1.0),
PyRunner(command='addPlotData()', iterPeriod=1000, label='graph'),
PyRunner(command='switchTranslationEngine()', iterPeriod=45000, nDo=2,
label='switchEng'),
]
## Generate flexible membrane
O.materials.append(CohFrictMat(young=1e7,poisson=1,density=2650,frictionAngle=radians(30),normalCohesion=3e7,shearCohesion=3e7,momentRotationLaw=True,label='gridNodeMat'))
O.materials.append( FrictMat(
young=1e7,poisson=0.1,density=2650,frictionAngle=radians(30),label='pFacetMat'
))
nodesIds=[]
cylIds=[]
pfacets=[]
width=2*r_cyl #diameter of cylinder
height=h_cyl #height of cylinder
nw=40 # no of nodes along perimeter
nh=25 # no of nodes along height
rNode=width/100 #radius of grid node
color1=[255./255.,102./255.,0./255.]
color2=[0,0,0]
color3=[248/255,248/255,168/255]
color4=[156/255,160/255,98/255]
rCyl2 = 0.5*width / cos(pi/float(nw))
vCenter = Vector3(x_cyl, y_cyl, 0)
for r in range(nw):
for h in range(nh):
v1 =
Vector3(rCyl2*cos(2*pi*(r+0)/float(nw)),rCyl2*sin(2*pi*(r+0)/float(nw)),
height*(h+0)/float(nh))+vCenter
v2 =
Vector3(rCyl2*cos(2*pi*(r+1)/float(nw)),rCyl2*sin(2*pi*(r+1)/float(nw)),
height*(h+0)/float(nh))+vCenter
v3 =
Vector3(rCyl2*cos(2*pi*(r+1)/float(nw)),rCyl2*sin(2*pi*(r+1)/float(nw)),
height*(h+1)/float(nh))+vCenter
v4 =
Vector3(rCyl2*cos(2*pi*(r+0)/float(nw)),rCyl2*sin(2*pi*(r+0)/float(nw)),
height*(h+1)/float(nh))+vCenter
V1=(O.bodies.append(gridNode(v1,rNode,wire=False,fixed=False,
material='gridNodeMat',color=color2)) )
V2=(O.bodies.append(gridNode(v2,rNode,wire=False,fixed=False,
material='gridNodeMat',color=color2)) )
V3=(O.bodies.append(gridNode(v3,rNode,wire=False,fixed=False,
material='gridNodeMat',color=color2)) )
V4=(O.bodies.append(gridNode(v4,rNode,wire=False,fixed=False,
material='gridNodeMat',color=color2)) )
# append node ids to seperate matrix for later use
nodesIds.append(V1)
nodesIds.append(V2)
nodesIds.append(V3)
nodesIds.append(V4)
#create grid connection
cylIds.append(O.bodies.append(gridConnection(V1,V2,rNode,material='gridNodeMat',color=color3)))
cylIds.append(O.bodies.append(gridConnection(V2,V3,rNode,material='gridNodeMat',color=color3)))
cylIds.append(O.bodies.append(gridConnection(V1,V3,rNode,material='gridNodeMat',color=color3)))
cylIds.append(O.bodies.append(gridConnection(V3,V4,rNode,material='gridNodeMat',color=color3)))
cylIds.append(O.bodies.append(gridConnection(V4,V1,rNode,material='gridNodeMat',color=color3)))
#create Pfacets
pfacets.append(O.bodies.append(pfacet(V1,V2,V3,wire=True,material='pFacetMat',color=color3)))
pfacets.append(O.bodies.append(pfacet(V1,V3,V4,wire=True,material='pFacetMat',color=color4)))
from yade import qt
qt.View()
r = qt.Renderer()
r.bgColor = 1, 1, 1
def addPlotData():
fMove = Vector3(0, 0, 0)
for i in top_plate:
fMove += O.forces.f(i)
plot.addData(z=O.iter, pMove=fMove[2], pFest=fMove[2])
def switchTranslationEngine():
print("Switch from TranslationEngine engine to ServoPIDController")
translat.dead = True
combEngine.dead = False
plot.plots = {'z': ('pMove', 'pFest')}
plot.plot()
O.run()
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