Question #693898 on Yade changed: https://answers.launchpad.net/yade/+question/693898
Status: Open => Answered Luc Scholtès proposed the following answer: Hi David, "What constitutive law would you recommend to achieve these cohesive bonds?" You can use the JCFPM. All interactions (onJoint or notOnJoint) can be defined with or without cohesion/tensile strength. The tensile strength defines a maximum admissible force in tension (normal direction to the contact). The cohesion defines a maximum admissible force in shear (tangential direction to the contact). Please find below an example for simulating a uniaxial compression test on an "intact" sample (no joints) with JCFPM. Luc --- # -*- coding: utf-8 -*- # -*- encoding=utf-8 -*- from yade import pack, plot ################# SIMULATIONS DEFINED HERE #### packing (previously constructed) OUT='compressionTest_JCFPM' #### Simulation Control rate=-0.01 #deformation rate iterMax=10000 # maximum number of iterations saveVTK=2000 # saving output files for paraview #### Material microproperties intR=1.1 # allows near neighbour interaction (can be adjusted for every packing) DENS=2500 # could be adapted to match material density: dens_DEM=dens_rock*(V_rock/V_particles)=dens_rock*1/(1-poro_DEM) -> packing porosity as to be computed? YOUNG=20e9 FRICT=7 ALPHA=0.1 TENS=1e6 COH=1e6 #### material definition def sphereMat(): return JCFpmMat(type=1,density=DENS,young=YOUNG,poisson=ALPHA,frictionAngle=radians(FRICT),tensileStrength=TENS,cohesion=COH) #### create the specimen pred=pack.inCylinder((0,0,0),(0,1,0),0.25) O.bodies.append(pack.regularHexa(pred,radius=0.025,gap=0.,material=sphereMat)) # up to you to define another sample here, e.g., with randomDensePack or anything else. R=0 Rmax=0 nbSpheres=0. for o in O.bodies: if isinstance(o.shape,Sphere): nbSpheres+=1 R+=o.shape.radius if o.shape.radius>Rmax: Rmax=o.shape.radius Rmean=R/nbSpheres print 'nbSpheres=',nbSpheres,' | Rmean=',Rmean #### boundary condition (see utils.uniaxialTestFeatures bb=utils.uniaxialTestFeatures() negIds,posIds,longerAxis,crossSectionArea=bb['negIds'],bb['posIds'],bb['axis'],bb['area'] ################# ENGINES DEFINED HERE O.engines=[ ForceResetter(), InsertionSortCollider([Bo1_Sphere_Aabb(aabbEnlargeFactor=intR,label='Saabb')]), InteractionLoop( [Ig2_Sphere_Sphere_ScGeom(interactionDetectionFactor=intR,label='SSgeom')], [Ip2_JCFpmMat_JCFpmMat_JCFpmPhys(cohesiveTresholdIteration=1,label='interactionPhys')], [Law2_ScGeom_JCFpmPhys_JointedCohesiveFrictionalPM(recordCracks=True,Key=OUT,label='interactionLaw')] ), UniaxialStrainer(strainRate=rate,axis=longerAxis,asymmetry=0,posIds=posIds,negIds=negIds,crossSectionArea=crossSectionArea,blockDisplacements=1,blockRotations=1,setSpeeds=0,stopStrain=0.1,dead=1,label='strainer'), GlobalStiffnessTimeStepper(active=1,timeStepUpdateInterval=10,timestepSafetyCoefficient=0.5, defaultDt=utils.PWaveTimeStep()), NewtonIntegrator(damping=0.4,label='newton'), PyRunner(iterPeriod=int(100),initRun=True,command='recorder()',label='data'), VTKRecorder(iterPeriod=int(saveVTK),initRun=True,fileName=OUT+'-',recorders=['spheres','jcfpm','cracks'],Key=OUT,label='vtk') ] ################# RECORDER DEFINED HERE def recorder(): yade.plot.addData({'i':O.iter, 'eps':strainer.strain, 'sigma':strainer.avgStress, 'tc':interactionLaw.nbTensCracks, 'sc':interactionLaw.nbShearCracks, 'te':interactionLaw.totalTensCracksE, 'se':interactionLaw.totalShearCracksE, 'unbF':utils.unbalancedForce()}) plot.saveDataTxt(OUT) # if you want to plot during simulation plot.plots={'i':('sigma')} plot.plot() ################# PREPROCESSING #### manage interaction detection factor during the first timestep and then set default interaction range ((cf. A DEM model for soft and hard rock, Scholtes & Donze, JMPS 2013)) O.step(); ### initializes the interaction detection factor SSgeom.interactionDetectionFactor=-1. Saabb.aabbEnlargeFactor=-1. #### coordination number verification numSSlinks=0 numCohesivelinks=0 for i in O.interactions: if isinstance(O.bodies[i.id1].shape,Sphere) and isinstance(O.bodies[i.id2].shape,Sphere): numSSlinks+=1 if i.phys.isCohesive : numCohesivelinks+=1 print "nblinks=", numSSlinks, " | nbCohesivelinks=", numCohesivelinks, " || Kcohesive=", 2.0*numCohesivelinks/nbSpheres ################# SIMULATION REALLY STARTS HERE strainer.dead=0 O.run(iterMax) -- You received this question notification because your team yade-users is an answer contact for Yade. _______________________________________________ Mailing list: https://launchpad.net/~yade-users Post to : yade-users@lists.launchpad.net Unsubscribe : https://launchpad.net/~yade-users More help : https://help.launchpad.net/ListHelp