**************************** Stress Free Solvent Vol Frac **************************** :: Stress Free Solvent Vol Frac = CONSTANT [] ----------------------- **Description / Usage** ----------------------- This required card is used to specify the model for the stress-free solvent volume fraction, which is the volume fraction of solvents in the solid material in its stress-free state. This card is used exclusively in materials of *LAGRANGIAN* or *TOTAL_ALE* Mesh Motion types (see *Mesh Motion* card) which are being modeled as gelled solids laden with solvent. At the gel-point, the solid is considered to be stress free, after which a reduction of solvent leads to volume shrinkage and hence a rising stress state. Definitions of the input parameters are as follows: +-----------------+------------------------------------------------------------------------------------------------------------------------------------+ |**CONSTANT** |Name of the model for the stress-free solvent volume fraction. | +-----------------+------------------------------------------------------------------------------------------------------------------------------------+ | |The value of the stress-free solvent volume fraction; this value is unitless. | +-----------------+------------------------------------------------------------------------------------------------------------------------------------+ ------------ **Examples** ------------ The following is a sample card: :: Stress Free Solvent Vol Frac = CONSTANT 0.5 This specification sets the volume fraction of solvent in the material to 50 per cent. That volume fraction is tantamount to the gel point of the material. ------------------------- **Technical Discussion** ------------------------- The stress free state volume fraction of solvent is basically the solvent fraction at which a material gels, viz., the state at which the material solidifies from a liquid state. This quantity is used in the continuity equation for incompressible solid materials, through which is transported by a variety of diffusion models (see *Diffusivity* card). The continuity equation, viz., *EQ = continuity*, is applied as follows: .. figure:: /figures/369_goma_physics.png :align: center :width: 90% where the dependent variable is the solid phase pressure (see *Solid Constitutive Equation* card). Here *det* **F** is the determinant of the deformation gradient tensor, yi is the volume fraction of component i (specified by the *EQ = species_bulk* card), and y0 is the volume fraction of total solvents at the stress free state. Clearly, as the solvent concentration decreases the local volume of solid decreases, creating a rising stress. -------------- **References** -------------- GT-001.4: GOMA and SEAMS tutorial for new users, February 18, 2002, P. R. Schunk and D. A. Labreche GT-019.1: Elastoviscoplastic (EVP) Constitutive Model in GOMA: Theory, Testing, and Tutorial, P. R. Schunk, A. Sun, S. Y. Tam (Imation Corp.) and K. S. Chen, January 11, 2001 SAND96-2149: Drying in Deformable Partially-Saturated Porous Media: Sol-Gel Coatings, Cairncross, R. A., P. R. Schunk, K. S. Chen, S. S. Prakash, J. Samuel, A. J. Hurd and C. Brinker (September 1996) .. TODO - Line 50 is a photo that needs to be replaced with the correct equation.