Dissipation in ElasticFoundationForce

[Hao Yang Chan]

Hi all, just wanted to ask how the dissipation coefficient within the ElasticFoundationForce is supposed to be derived from desired materials. Thanks!

[Emil Walczak]

Hi, here you have the publication about contact in OpenSim.

[Michael Sherman]

That paper explain how the dissipation coefficient is used but probably doesn't provide enough information to figure out what it should be.

There is some theory for choosing this coefficient from coefficient-of-restitution vs. impact velocity experiments. I think in practice though the best approach is to create a very simple model with a simple contact shape (a sphere, for example) and run a few virtual experiments with different coefficients to obtain roughly the expected behavior. Then use the resulting material properties in your more complex model.

Does anyone else have practical advice for choosing this coefficient?

Sherm

[Hao Yang Chan]

As of right now I'm simulating the femur and tibia with ligaments attached undergoing shear, torque and compression at the joint. The stiffness is roughly as it should be - (1762 GPa)/(0.01 m). I set the dissipation factor to 0.8 to avoid any excessive bouncing of the femur (the tibia is locked in 3 space).