by Hartmueller » Thu Apr 21, 2011 1:03 pm
Hello,
i have a question about the Hertz-Mindlin contact Model. I used the UDL source code and modified it in one point. I implemented a data output in a txt file to check the acting forces, especially, the elastic restitution force called F_n in the source code.
Then i created an experimental setup. I created a Particle with radius 0.0007 in a very short distance over a plate. The Particle fell down, bounced back some times and after that it stayed in the same position. The acting F_n at this moment had exactly the same value as the particles weight.
Then i let the plate vibrated with a frequency of 1000 Hz and an amplitude of 0.0001 m. When i calculate the maximum acceleration because of the vibration it should be about 3950 m/s² ( a_max = (2 * Pi * f)² * A ).
So the maximum force acting on the particle should be F_vibr = a_mx * m_particle (the particle density was 2436 kg/m², so the mass was about 3.5E-06 kg). I calculated a value of 0,01381 N.
As i checked the output file i found a maximum F_n of 1.0204 N, which is about 73 times higher than i calculated before. The timestep of the simulation was 0.5E-09.
How could this be explained?
Thanks