Hertz Mindlin Contact Model

For discussing contact models, particle body forces and custom factories written using the EDEM API

Hertz Mindlin Contact Model

Postby Mark » Mon Jan 24, 2011 9:03 pm

Here you will find the UDL source code for an example of the Hertz Mindlin contact model built in to EDEM:
http://www.dem-solutions.com/support/files/examples/HertzMindlin.zip

Package also includes an example situation which simulates a simple screw auger.

Image

Please take a look at the code for your own project and remember to come back and post up any modifications or code snippets which will help other users along the way. Feel free to use this forum for asking questions about this contact model.

DEM Solutions Team.
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Re: Hertz Mindlin Contact Model

Postby 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
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Re: Hertz Mindlin Contact Model

Postby Stephen » Thu Apr 21, 2011 5:51 pm

Can this be explained by the timestep used? If you run the same simulation with a lower timestep do you get the same results?
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