Main Help → All Commands → Diffusion Calculations → Diffusion
The Diffusion
command activates generalized diffusion-style calculations.
Diffusion (style),<(conc0)>,<(nolimit)>
where
(style)
is the type of diffusion calculations to include in the MPM analysis with the options being:
When doing "solvent" diffusion, the calculations use a "concentration potential" defined as c/csat
where (csat)
is a "reference" (or "saturation") concentration defined in material properties. The two optional parameters apply only when modeling "solvent" diffusion:
(conc0)
defines a stress-free concentration potential that corresponds to zero concentration-induced strain. Any material points that do not have they concentration set, will set their concentration potential to (conc0)
.
(nolimit)
: by default a material's reference concentration is defined as a saturation or maximum concentration and the potential must be between 0 and 1. If this parameter is 1 (or the text "nolimit"), the potential is allowed to have any non-negative value. In this mode, a material's (csat)
is an arbitrary (nonzero) reference value such a a 1 mole per unit volume.When solvent diffusion calculations are activated, you must define diffusion constants of the materials used in the analysis. Diffusion is coupled to strains through concentration-induced expansion, but only if you enter non-zero values for concentration expansion coefficients when defining the materials.
Other diffusion options can be used with or without solvent diffusion. Their use depends on material support for their calculations and you must define any required material properties.
(style)=2
corresponds to poroelasticity calculations, but they should be activated instead with a poroelasticity command.Diffusion
command is only allowed for MPM analyses.