Question #211358 on Yade changed: https://answers.launchpad.net/yade/+question/211358
Status: Open => Answered Jan Stránský proposed the following answer: Hello Christian, how do you measure the force in your experiment? how looks ground in your experiment? I would say that the simulation is much stiffer than reality (the ground sphere is perfectly fixed, which is not present in reality), therefore you get higher force in simulation. Also note that FrictMat.young differs from real Young modulus of material, but this is not the source of such huge error. To obtain better results in the contact phase, I would decrease the time step. So in my opinion the problem is in assumption of equivalency between the experiment and simulation (I did some simple analytical solution of your simulation and the force was 440N, so the simulation itself is ok). good luck Jan 2012/10/16 Christian Sommerfeld <question211...@answers.launchpad.net> > New question #211358 on Yade: > https://answers.launchpad.net/yade/+question/211358 > > Hi, > > i want to validate a simple test with 2 balls. But i get a force in my > simulation which is so much higher than the force of the real test. So i > take a look in my code for 2 days but i can't find any mistake. > > The experiment: The first ball has the material porcelain and this ball > falls down from a high of 0,1 m with the normal gravity 9,81. At the point > (0,0,0) is the second ball which has teh material steel and this ball is > fixed. In the real experimentr i get for the approach a force of 6 N in the > direction of movement. For the simulazion i use the SI- units for all of > my parameters to make it as easy as possible. But i get a force of 350 N > and i do know why? > > > from yade import plot, geom, utils > > O.materials.append(FrictMat(young=210e9,poisson=0.3,frictionAngle=.5,density=7900, > label='mat_ground')) > > O.materials.append(FrictMat(young=90e9,poisson=0.14,frictionAngle=.5,density=2500, > 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=0.2, 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()) > > plot.plots={'t':('F')} > plot.plot() > > from yade import qt > v=qt.View() > > -- > 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 : yade-users@lists.launchpad.net > Unsubscribe : https://launchpad.net/~yade-users > More help : https://help.launchpad.net/ListHelp > -- 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 : yade-users@lists.launchpad.net Unsubscribe : https://launchpad.net/~yade-users More help : https://help.launchpad.net/ListHelp