Hello,

I am trying to use Houdini to simulate the behavior of 3D printing materials that we can characterize, mechanically, in my lab.

Is there any detailed documentation on the model(s) that Houdini uses for the FEM module?
Specifically, I would like to know the constitutive model or spring-dashpot model and how the variables shape stiffness, volume stiffness, and damping ratio are reflected in said model. The help/online documentation is very very very high-level.

If anyone is interested in this, here is what I have found so far:

1. From the Houdini doc. on Setting up finite elements [www.sidefx.com], we get this key piece of info.

If the material model is isotropic (Enable Anisotropy is turned off), then the Volume Stiffness and the Shape Stiffness are related to the Lamé parameters. If you know Lamé’s first and second parameter for the material that you want to model, then you can set Volume Stiffness to Lamé’s first parameter and you can set Shape Stiffness to Lamé’s second parameter times two.

2. From solid mechanics [en.wikipedia.org], we know that the linear response of “hookean solids” is given by the equation:

In this equation: \sigma is the stress in the material, \epsilon is the engineering strain, \lambda is the 1st Lame parameter (equivalent to the volume stiffness), and \mu is the 2nd Lame parameter (equivalent to the shape stiffness).

This is great if you can fit your date to this relatively simple model!