Proper Simulation for Silicone/Rubber like materials (elastomers)
Hi @kevinmamaqi,
Elastomers, while fully elastic, have nonlinear stress-strain behavior. So, you need to consider the strain history and the change in geometry. A linear static stress analysis does not provide the required functionality. However, nonlinear static stress and event simulation analyses do. Each of these study types involves incremental calculations in which the geometry and strain are updated over time. That's half of the battle. The second half is that a hyperelastic material model is required to properly define the nonlinear material behavior.
A hyperelastic material model is currently in development and will be available in an upcoming release of Fusion 360. This hyperelastic model provides a means of adding advanced materials to the Favorites library (and optionally to a user-created library) defined according to the standard 2-coefficient Mooney-Rivlin hyperelastic material model. The implementation in Fusion 360 will be for nearly incompressible materials, which introduces a third constant (based on the bulk modulus) needed to define the material's volumetric deformation. You can define a high value for this third constant to approximate incompressible behavior.
When this new material model is released, the Help will include the necessary details regarding the Mooney-Rivlin strain energy function and the definition of the necessary constants. The procedure for creating hyperelastic materials in the library will also be added to the Help.
Mooney-Rivlin constants are generated using a curve-fitting routine and are based on raw stress-strain data from lab tests. There are a number of material curve fitting routines that are commercially available for performing this function. Once the constants are determined, simply create a hyperelastic material in Fusion 360, specify the three constants, specify the density, and the material is ready to be used within a nonlinear simulation study.
Regards,
-Joe
