You can use the Edit Material dialog box to define certain aspects of mass diffusion. See the following sections for details:
Diffusivity defines the diffusion, or movement, of one material through another. The governing equations for mass diffusion are an extension of Fick's equations: they allow for nonuniform solubility of the diffusing substance in the base material and for mass diffusion driven by gradients of temperature and pressure. See the following sections for more information:
“Diffusivity,” Section 26.4.1 of the Abaqus Analysis User's Guide
“Mass diffusion analysis,” Section 6.9.1 of the Abaqus Analysis User's Guide
To define diffusivity:
From the menu bar in the Edit Material dialog box, select OtherMass DiffusionDiffusivity.
(For information on displaying the Edit Material dialog box, see “Creating or editing a material,” Section 12.7.1.)
Click the arrow to the right of the Type field, and specify the directional dependence of the diffusivity.
Select a Law option to specify how you want to define diffusivity behavior:
Select General to choose general mass diffusion behavior.
Select Fick to choose Fick's diffusion law.
Toggle on Use temperature-dependent data to define diffusivity data as a function of temperature.
A column labeled Temp appears in the Data table.
Click the arrows to the right of the Number of field variables field to increase or decrease the number of field variables on which the diffusivity data depend.
In the Data table, enter the applicable data:
D
Isotropic diffusivity. (Units of L2T–1.)
D11, D22, and D33
Orthotropic diffusivity terms. (Units of L2T–1.)
D11, D12, D22, D13, D23, D33
Anisotropic diffusivity terms. (Units of L2T–1.)
Concentration
Mass concentration of the diffusing material.
Temp
Temperature.
Field n
Predefined field variables.
To describe temperature-driven diffusion, select Soret Effect from the Suboptions menu. (This option is valid only if you selected General in Step 3.) See “Defining general temperature-driven mass diffusion” for detailed instructions.
To describe pressure-driven mass diffusion, select Pressure Effect from the Suboptions menu. See “Defining pressure-driven mass diffusion” for detailed instructions.
Click OK to close the Edit Material dialog box. Alternatively, you can select another material behavior to define from the menus in the Edit Material dialog box (see “Browsing and modifying material behaviors,” Section 12.7.2, for more information).
The Soret effect factor, , governs temperature-driven mass diffusion. You can define the Soret effect factor as a function of concentration, temperature, and/or field variables. See “Diffusivity,” Section 26.4.1 of the Abaqus Analysis User's Guide, for more information.
Note: You can specify the Soret effect factor only if you select general mass diffusion behavior in the diffusivity definition. (If you select Fick's diffusion law, the Soret effect factor is calculated automatically.) For more information, see “Fick's law” in “Mass diffusion analysis,” Section 6.9.1 of the Abaqus Analysis User's Guide.
To define the Soret effect factor:
Define diffusivity as described in “Defining diffusivity.”
From the Suboptions menu in the Edit Material dialog box, select Soret Effect.
A Suboption Editor appears.
Toggle on Use temperature-dependent data to define the Soret effect factor as a function of temperature.
A column labeled Temp appears in the Data table.
Click the arrows to the right of the Number of field variables field to increase or decrease the number of field variables included in the definition of the Soret effect factor.
Enter the following data in the Data table:
kappa_s
Soret effect factor, . (Units of F1/2L–1.)
Concentration
Mass concentration of the diffusing material.
Temp
Temperature.
Field n
Predefined field variables.
Click OK to return to the Edit Material dialog box.
The pressure stress factor, , governs mass diffusion driven by the gradient of the equivalent pressure stress. You can define the pressure stress factor as a function of concentration, temperature, and/or field variables. See “Diffusivity,” Section 26.4.1 of the Abaqus Analysis User's Guide, for more information.
To define the pressure stress factor:
Define diffusivity as described in “Defining diffusivity.”
From the Suboptions menu in the Edit Material dialog box, select Pressure Effect.
A Suboption Editor appears.
Toggle on Use temperature-dependent data to define the pressure stress factor as a function of temperature.
A column labeled Temp appears in the Data table.
Click the arrows to the right of the Number of field variables field to increase or decrease the number of field variables included in the definition of the pressure stress factor.
Enter the following data in the Data table:
kappa_p
Pressure stress factor, . (Units of LF–1/2.)
Concentration
Mass concentration of the diffusing material.
Temp
Temperature.
Field n
Predefined field variables.
Click OK to return to the Edit Material dialog box.
Solubility, s, is used to define the “normalized concentration,” , of the diffusing phase in a mass diffusion process:
“Diffusivity,” Section 26.4.1 of the Abaqus Analysis User's Guide
“Mass diffusion analysis,” Section 6.9.1 of the Abaqus Analysis User's Guide
To define solubility:
From the menu bar in the Edit Material dialog box, select OtherMass DiffusionSolubility.
(For information on displaying the Edit Material dialog box, see “Creating or editing a material,” Section 12.7.1.)
Toggle on Use temperature-dependent data to define solubility as a function of temperature.
A column labeled Temp appears in the Data table.
Click the arrows to the right of the Number of field variables field to increase or decrease the number of field variables on which the solubility depends.
Enter the following data in the Data table:
Solubility
Solubility. (Units of PLF–1/2.)
Temp
Temperature.
Field n
Predefined field variables.
Click OK to close the Edit Material dialog box. Alternatively, you can select another material behavior to define from the menus in the Edit Material dialog box (see “Browsing and modifying material behaviors,” Section 12.7.2, for more information).