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[Fu zuoguang <question231380@xxxxxxxxxxxxxxxxxxxxx>]

New question #231380 on Yade:
https://answers.launchpad.net/yade/+question/231380

Dear Christian Jakob and all users:
     Thanks for the suggestions you gave me. So I have taken a correct running of my 2D biaxial compression simulation but still have some questions about the curve of deviatoric stress versus axial strain. The link of my result image is http://i.imgur.com/TRgetm4.jpg.
     As a student DEM researcher, lack of experience makes me hard to understand this result, in which the values of deviatoric stress are not smooth, that can fluctuate with the increase of axial-strain. But in this paper "DEM Modeling and Geotechnical Applications" from Bruno Chareyre, the same curve can be described as http://i.imgur.com/cgd7UHR.jpg.
     This paper notice that the difference between the quasistatic limit and the apparent peak stress from the simulation can be controlled if the strain rate is small enough. But I think that the strain rate is not the only reason for this problem occuring, there may be some other factors that can effect this result such as material, confining pressure, damping, contact law or calculation step. So I upload some important details of my whole script and ask your help!

##################################################################################################
(1).material def:
clumpsmat = O.materials.append(FrictMat(poisson=0.5,density=250000,young=1e10,frictionAngle=0.5))
wallmat = O.materials.append(FrictMat(poisson=0.5,density=250000,young=1e10,frictionAngle=0))
##################################################################################################
(2).confining def:
triax01=TriaxialStressController(
	wall_bottom_id=wallids[2],wall_top_id=wallids[3],
	wall_left_id=wallids[0],wall_right_id=wallids[1],
	wall_back_id=wallids[4],wall_front_id=wallids[5],
	wall_front_activated = False,wall_back_activated = False,
	internalCompaction=False, 
	stressMask=7,
        goal1=50000,
        goal2=50000,
        goal3=50000,
        max_vel=5,
)##################################################################################################
(3).2D biaxial compression def:
triax02=TriaxialStressController(
	wall_bottom_id=wallids[2],wall_top_id=wallids[3],
	wall_left_id=wallids[0],wall_right_id=wallids[1],
	wall_back_id=wallids[4],wall_front_id=wallids[5],
	wall_front_activated = False,wall_back_activated = False,
	internalCompaction=False, 
	stressMask = 5,
        goal2= -0.1,
        goal1=50000,
        goal3=50000,
)#################################################################################################
(4)engine def:
O.engines=[
	ForceResetter(),
	InsertionSortCollider([Bo1_Sphere_Aabb(),Bo1_Box_Aabb(),Bo1_Wall_Aabb()]),
	InteractionLoop(
		[Ig2_Sphere_Sphere_ScGeom(),Ig2_Box_Sphere_ScGeom()],
		[Ip2_FrictMat_FrictMat_FrictPhys()],
		[Law2_ScGeom_FrictPhys_CundallStrack()]
	),
	GlobalStiffnessTimeStepper(active=1,timeStepUpdateInterval=100,timestepSafetyCoefficient=0.8),
	triax02,
	NewtonIntegrator(damping=.4),
]################################################################################################
(5).calculation step def:
dt = 1e-4 (but not working, it uses "p-wave" and the value of it in simulation is 6.6e-6)
#################################################################################################

How to modify these parameters, seeking your help!

      

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