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[liukeqi <question303013@xxxxxxxxxxxxxxxxxxxxx>]

New question #303013 on Yade:
https://answers.launchpad.net/yade/+question/303013

Hi, everyone 
  I want to use the engine Peri3dController to reach the goal state, but I suffered some question. I used the identical initial condition, and used two ways to reach the same goal of strain, but I got different results. The first way is that I used the stressMask=0b011100 and goal=(0,-8e-4,0,0,0,0) and nSteps = 8000 to compute once. The second way is that I used the stressMask=0b011100 and goal=(0,-4e-4,0,0,0,0) and nSteps = 4000 to compute twice by using strain=p3d.strain(imitating the example peri3dController_triaxialCompression.py ). I thought that the final goal is same, and the rate of applied strain is also same (goal/nSteps), so the final stress should be same, too, should not it? But the final stress is different! The following is my code, can you give me some suggestions? Thank you.

##################################### The initial condition
#!/usr/bin/python           # This is server.py file
import string
from yade import plot,qt
from yade.pack import *
from yade import pack, plot

O.materials.append(CpmMat(young=150e9,frictionAngle=atan(0.8),poisson=.2,sigmaT=500e8,epsCrackOnset=1e-6,relDuctility=80000))

initSize=1.2

sp=pack.randomPeriPack(radius=.05,initSize=Vector3(initSize,initSize,initSize))

sp.toSimulation()

O.save('/tmp/tt.gz')

################################# The first way, using goal=-8e-4 and nSteps=8000 to compute once
#!/usr/bin/python           # This is server.py file
import string
from yade import plot,qt
from yade.pack import *
from yade import pack, plot

loadFile='/tmp/tt.gz'
O.load(loadFile)

O.dt=PWaveTimeStep()/2

plot.plots={'ex':('sx',)}
def plotAddData():
	plot.addData(
		sx=p3d.stress[1],
		ex=p3d.strain[1],
	)

EnlargeFactor=1.5
EnlargeFactor=1.0
O.engines=[
	ForceResetter(),
	InsertionSortCollider([Bo1_Sphere_Aabb(aabbEnlargeFactor=EnlargeFactor,label='bo1s')]),
	InteractionLoop(
		[Ig2_Sphere_Sphere_ScGeom(interactionDetectionFactor=EnlargeFactor,label='ig2ss')],
		[Ip2_CpmMat_CpmMat_CpmPhys()],[Law2_ScGeom_CpmPhys_Cpm()]),
	NewtonIntegrator(),
	Peri3dController(
					
							nSteps=8000, 			# how many time steps the simulation will last
							# after reaching nSteps do doneHook action
							doneHook='print "Simulation with Peri3dController finished."; O.pause()',

							# the prescribed path (step,value of stress/strain) can be defined in absolute values
							
							# or in relative values
							
							# if the goal value is 0, the absolute stress/strain values are always considered (step values remain relative)plot.plots={'ex':('sx',)}
							
							# if ##Path is not explicitly defined, it is considered as linear function between (0,0) and (nSteps,goal)
							# as in yzPath and xyPath
							# the relative values are really relative (zxPath gives the same - except of the sign from goal value - result as yyPath)
							
							
							# variables used in the first step
							label='p3d'
							),
	PyRunner(command='plotAddData()',iterPeriod=1),
]



p3d.stressMask=0b011100       # prescribed ex,ey,sz,syz,ezx,sxy;   e..strain;  s..stress
p3d.goal=(0,-0.008,0,0,0,0)  #xx, yy, zz, yz, zx, xy
O.step()
bo1s.aabbEnlargeFactor=ig2ss.interactionDetectionFactor=1.
O.run(); O.wait()


print "p3d.stress[0]"
print p3d.stress[0]
print "p3d.stress[1]"
print p3d.stress[1]
print "p3d.stress[5]"
print p3d.stress[5]


plot.saveDataTxt('8000.txt')	
plot.plot(subPlots=False)


####################################### The second way, using goal=-4e-4 and nSteps=4000 and strain=p3d.strain to compute twice
#!/usr/bin/python           # This is server.py file
import string
from yade import plot,qt
from yade.pack import *
from yade import pack, plot


loadFile='/tmp/tt.gz'
O.load(loadFile)

 
O.dt=PWaveTimeStep()/2

plot.plots={'ex':('sx',)}
def plotAddData():
	plot.addData(
		sx=p3d.stress[1],
		ex=p3d.strain[1],
	)

EnlargeFactor=1.5
EnlargeFactor=1.0
O.engines=[
	ForceResetter(),
	InsertionSortCollider([Bo1_Sphere_Aabb(aabbEnlargeFactor=EnlargeFactor,label='bo1s')]),
	InteractionLoop(
		[Ig2_Sphere_Sphere_ScGeom(interactionDetectionFactor=EnlargeFactor,label='ig2ss')],
		[Ip2_CpmMat_CpmMat_CpmPhys()],[Law2_ScGeom_CpmPhys_Cpm()]),
	NewtonIntegrator(),
	Peri3dController(
					
							nSteps=4000, 			# how many time steps the simulation will last
							# after reaching nSteps do doneHook action
							doneHook='print "Simulation with Peri3dController finished."; O.pause()',

							# the prescribed path (step,value of stress/strain) can be defined in absolute values
							
							# or in relative values
							
							# if the goal value is 0, the absolute stress/strain values are always considered (step values remain relative)plot.plots={'ex':('sx',)}
							
							# if ##Path is not explicitly defined, it is considered as linear function between (0,0) and (nSteps,goal)
							# as in yzPath and xyPath
							# the relative values are really relative (zxPath gives the same - except of the sign from goal value - result as yyPath)
							
							
							# variables used in the first step
							label='p3d'
							),
	PyRunner(command='plotAddData()',iterPeriod=1),
]



p3d.stressMask=0b011100       # prescribed ex,ey,sz,syz,ezx,sxy;   e..strain;  s..stress
p3d.goal=(0,-0.004,0,0,0,0)  #xx, yy, zz, yz, zx, xy
O.step()
bo1s.aabbEnlargeFactor=ig2ss.interactionDetectionFactor=1.
O.run(); O.wait()



O.engines=[
				ForceResetter(),
				InsertionSortCollider([Bo1_Sphere_Aabb(aabbEnlargeFactor=1.0)]),
				InteractionLoop(
					[Ig2_Sphere_Sphere_ScGeom(interactionDetectionFactor=1.0)],
					[Ip2_CpmMat_CpmMat_CpmPhys()],[Law2_ScGeom_CpmPhys_Cpm()]),
				NewtonIntegrator(),
				Peri3dController(
									 	# Vector6 of prescribed final values (xx,yy,zz, yz,zx,xy)
										stressMask=0b011100,    # prescribed ex,ey,sz,syz,ezx,sxy; 
										nSteps=4000, 			# how many time steps the simulation will last
										# after reaching nSteps do doneHook action
										doneHook='print "Simulation with Peri3dController finished."; O.pause()',

										# the prescribed path (step,value of stress/strain) can be defined in absolute values
							
										# or in relative values
							
										# if the goal value is 0, the absolute stress/strain values are always considered (step values remain relative)
							
										# if ##Path is not explicitly defined, it is considered as linear function between (0,0) and (nSteps,goal)
										# as in yzPath and xyPath
										# the relative values are really relative (zxPath gives the same - except of the sign from goal value - result as yyPath)
							
							
										# variables used in the first step
										label='p3d',
										strain=p3d.strain
										),
				PyRunner(command='plotAddData()',iterPeriod=1),
			
			]

p3d.goal=(0,-0.004,0,0,0,0)   
print p3d.goal
O.run();O.wait()




print "p3d.stress[0]"
print p3d.stress[0]
print "p3d.stress[1]"
print p3d.stress[1]
print "p3d.stress[5]"
print p3d.stress[5]


plot.saveDataTxt('4000.txt')	
plot.plot(subPlots=False)




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