Hygroscopic Swelling
Hygroscopic swelling is an internal strain caused by changes in moisture content. This strain can be written as
where βh is the coefficient of hygroscopic swelling, cmo is the moisture concentration, and cmo,ref is the strain-free reference concentration. It is possible to model bending due to a concentration gradient in the transverse directions of the beam. The concentration is then assumed to vary linearly through the thickness.
Model Inputs
From the Concentration c list, select an existing concentration variable from another physics interface, if any concentration variables exist. For User defined enter a value or expression for the concentration. This is the centerline concentration of the beam, controlling the axial part of the hygroscopic swelling.
The unit for the input depends on the setting of Concentration type in the Hygroscopic Swelling Properties section. Only concentration variables having the chosen physical dimension are available in the Concentration list.
Hygroscopic Swelling Properties
In the Concentration type list, select Molar concentration (the default) or Mass concentration, depending on the units used for the concentration.
Enter a Strain reference concentration cref. This is the concentration at which there are no strains due to hygroscopic swelling.
If Molar concentration is selected as Concentration type, also enter the Molar mass of the fluid, Mm. The default value is 0.018 kg/mol, which is the molar mass of water.
The default Coefficient of hygroscopic swelling βh uses values From material. For User defined select Isotropic (the default), Diagonal, or Symmetric to enter one or more components for a general coefficient of hygroscopic swelling tensor βh.The default value for the User defined case is 1.5e-4 m3/kg.
Hygroscopic Bending
Enter the Concentration gradient in local y direction cgy (in 2D and 3D) and in the Concentration gradient in local z direction cgz (in 3D), which affects the hygroscopic bending. If beam cross section dimensions have been defined at Bending stress evaluation pointsFrom section heights, these could be used in an expression containing the concentration difference.
Location in User Interface
Context Menus
Ribbon
Physics tab with Linear Elastic Material node selected in the model tree: