Question #211358 on Yade changed: https://answers.launchpad.net/yade/+question/211358
Christian Sommerfeld posted a new comment: Hi, @Chareyre: i measured the force with a load cell. I did a Calculation of the normal force and i get a force of 365 N. But this is not the force i want to measure. So i took a look on the wiki page of contact mechanics http://en.wikipedia.org/wiki/Contact_mechanics So i implemented the force into my code and i get nearly the force that i'm looking for. from yade import plot, geom, utils #parameters: r1 = 0.003 r2 = 0.003 E1 = 210e9 E2 = 90e9 poisson1 = 0.3 poisson2 = 0.14 frictionAngle = .5 density1 = 7900 density2 = 2500 g = 9.81 h = 0.1 #computation: k1 = 2*E1*r1 k2 = 2*E2*r2 kn = (k1*k2)/(k1+k2) V1 = 4.0/3.0*math.pi*r1*r1*r1 V2 = 4.0/3.0*math.pi*r2*r2*r2 #m1 = density1*V1 m2 = density2*V2 m1 = 0.0004 Epot = m1*g*h d = ((2*Epot)/kn)**(1/2.0) Etot = 1.0/((1.0-poisson1**(2.0))/E1+((1.0-poisson2**(2.0))/E2)) Fres = 4.0/3.0*Etot*r1**(1.0/2.0) O.materials.append(FrictMat(young=E1,poisson=poisson1,frictionAngle=frictionAngle,density=density1, label='mat_ground')) O.materials.append(FrictMat(young=E2,poisson=poisson2,frictionAngle=frictionAngle,density=density2, label='mat_spheres')) O.bodies.append(utils.sphere([0,0,0.103],0.003,color=[1,1,0], material='mat_spheres')) O.bodies.append(utils.sphere([0,0,0.003],0.003,color=[1,1,1], fixed=True, material='mat_ground')) O.engines=[ ForceResetter(), InsertionSortCollider([Bo1_Sphere_Aabb(),Bo1_Facet_Aabb()]), InteractionLoop( [Ig2_Sphere_Sphere_ScGeom(),Ig2_Facet_Sphere_ScGeom()], [Ip2_FrictMat_FrictMat_FrictPhys()], [Law2_ScGeom_FrictPhys_CundallStrack()] ), NewtonIntegrator(damping=0.5, gravity=(0,0,-9.81)), PyRunner(iterPeriod=5,command="myAddPlotData()") ] O.dt=1*utils.PWaveTimeStep() def myAddPlotData(): force=plot.addData(t=O.time,F=(O.forces.f(0).norm()/kn)**(3.0/2.0)*Fres) plot.plots={'t':('F')} plot.plot() from yade import qt v=qt.View() Now i have two question: 1. What is the physical meaning of the normal force from cundall and strack? Why is that force so high for a ball with a radius of 3 mm 2. If i want to calculate the normal stiffness kn i need a length proportional to the radius from both bodies. Like for a sphere k=E*2*r. How can i obtain this lenght for a facetcylinder? Is this the radius of the base? -- You received this question notification because you are a member of yade-users, which is an answer contact for Yade. _______________________________________________ Mailing list: https://launchpad.net/~yade-users Post to : [email protected] Unsubscribe : https://launchpad.net/~yade-users More help : https://help.launchpad.net/ListHelp
