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[Jan Stránský <question290372@xxxxxxxxxxxxxxxxxxxxx>]

Question #290372 on Yade changed:
https://answers.launchpad.net/yade/+question/290372

    Status: Open => Answered

Jan Stránský proposed the following answer:
Hi Mohsen,

see the links below. For the same radius R:
E = .5*(young1+young2)
kn = pi*r^2*E/distance

cheers
Jan

[1] https://yade-dem.org/doc/formulation.html#normal-stiffness
[2]
http://bazaar.launchpad.net/~yade-pkg/yade/git-trunk/view/head:/pkg/dem/ConcretePM.cpp#L77
[3]
http://bazaar.launchpad.net/~yade-pkg/yade/git-trunk/view/head:/pkg/dem/ConcretePM.cpp#L321


2016-04-10 14:52 GMT+02:00 mohsen <question290372@xxxxxxxxxxxxxxxxxxxxx>:

> New question #290372 on Yade:
> https://answers.launchpad.net/yade/+question/290372
>
> In the name of god
> hello all
> during an script i make contact between two spheres of Cpm material but
> the different parameters. There are two bouncing spheres.  Then i checked
> O.interactions two see the contact parameters. I do not know how the young
> modulus of contact has been computed?
>  any idea?
>
> Thanks every one
> #####
>
> mat2=CpmMat(young=1e6,neverDamage=True,density=2500,poisson=0.2,epsCrackOnset=1e20,relDuctility=10,frictionAngle=0.5,label='mat2')
> O.materials.append(mat2)
>
> O.materials.append(CpmMat(young=1e12,neverDamage=True,poisson=0.3,frictionAngle=radians(30),sigmaT=4e100,epsCrackOnset=1e20,density=2600,relDuctility=10,label='mat1'))
>
> O.bodies.append([
>
> sphere(center=(0,0,0),radius=.5,fixed=True, material='mat1'),
>
> sphere((0,0,2),.5, material='mat2')
> ])
>
> intRadius = 1
> O.engines = [
> ForceResetter(),
>
> InsertionSortCollider([Bo1_Sphere_Aabb(aabbEnlargeFactor=intRadius,label='is2aabb'),Bo1_Facet_Aabb(),Bo1_Wall_Aabb()]),
> InteractionLoop(
>
> [Ig2_Sphere_Sphere_ScGeom(interactionDetectionFactor=intRadius,label='ss2d3dg'),Ig2_Facet_Sphere_ScGeom(),Ig2_Wall_Sphere_ScGeom()],
> [Ip2_CpmMat_CpmMat_CpmPhys()],
> [Law2_ScGeom_CpmPhys_Cpm()]
> ),
> NewtonIntegrator(gravity=(0,0,-10),damping=0.2),
> ]
> O.dt = .2*PWaveTimeStep()
> #########
>
> The interaction specifications:
>
> {'E': 500000500000.0,
>  'G': 175000175000.0,
>  'crossSection': 0.7853981633974483,
>  'damLaw': 1,
>  'dmgOverstress': 0.0,
>  'dmgRateExp': 0.0,
>  'dmgStrain': 0.0,
>  'dmgTau': -1.0,
>  'epsCrackOnset': 1e+20,
>  'epsFracture': 1e+21,
>  'isCohesive': False,
>  'isoPrestress': 0.0,
>  'kn': 392699474749.80115,
>  'ks': 137444816162.43042,
>  'neverDamage': True,
>  'normalForce': Vector3(0,0,-7853.981599551652),
>  'plRateExp': 0.0,
>  'plTau': -1.0,
>  'refLength': 0.9999999991036522,
>  'refPD': 8.963477737822245e-10,
>  'relDuctility': 10.0,
>  'shearForce': Vector3(-0,-0,-7.623695394542987e-13),
>  'tanFrictionAngle': 0.9538822108108043,
>  'undamagedCohesion': 2e+100}
>
>
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