The last model you shared uses a Static Structural analysis, but since you want to include Coupled Pore-Fluid Diffusion and Structural Model of Porous Media, you might want to select the Coupled Field Static analysis from the toolbox. Read Chapter 2.12 to learn how to perform this type of analysis.
The material models supported in the coupled structural-pore-fluid-diffusion analysis include elasticity (isotropic, orthotropic and anisotropic), porous elasticity, Mohr Coulomb plasticity, Cam-clay plasticity, jointed rock plasticity, extended Drucker-Prager and Drucker-Prager-based concrete plasticity.
Porous elasticity material can be defined with an Initial void ratio, which would be 0.45 to give you a solid volume fraction of 0.55
Note that Hyperelastic material models are not on the list of material that support pore-fluid diffusion. I don’t know where you want the pore-fluid diffusion to act, but you have used Hyperelastic materials such as Yeoh for Piamater and Duramater, Mooney-Revlin for Sclera and Neo-Hookean for Choroid. However, I find in Engineering Data, it does not complain if I add Porous Elasticity to a Neo-Hookean material, but maybe they just haven’t put all the error checking in that is required. For many illegal combinations, Engineering Data will use a strike-though font so highlight illegal combinations in material properties.
Note that you must mesh the bodies that will have permeability with the correct element type that supports coupled pore pressure analysis such as CPT217.
There are two Verification Test models of coupled pore-pressure deformations. One is a 2D model VM260. VM264 is a 3D model using CPT217. I see they use Analysis Type of Static (ANTYPE,0) so maybe you don’t have to use ANTYPE,SOIL which was mentioned in 2.12 above.
In the last model you sent, I see the volume changes in Step 1, but not in Steps 2 and 3. Maybe when you get a model that includes pore-fluid diffusion, you will see a volume change.
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