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 thickness direction of the shell. The concentration is then assumed to vary linearly through the thickness.
Layer Selection
This section is only present when this node is added under Layered Linear Elastic Material node. In this section, select the layers in which hygroscopic swelling needs to be modeled.
For a general description of this section, see Layer Selections in the documentation for the Composite Materials Module.
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 midsurface concentration in the shell, controlling the membrane 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. When a nonisotropic coefficient of hygroscopic swelling is used, the axis orientations are given by the coordinate system selection in the parent node.
The Include moisture as added mass check box is selected by default. When selected, the mass of the fluid is included in a dynamic analysis, and when using mass proportional loads. It will also contribute when computing mass properties.
Hygroscopic Bending
Enter the Concentration difference in thickness direction Δcgy, which affects the hygroscopic bending. This is the difference between the concentrations at the top and bottoms surfaces.
Location in User Interface
Context Menus
Shell>Linear Elastic Material>Hygroscopic Swelling
Shell>Layered Linear Elastic Material>Hygroscopic Swelling
Plate>Linear Elastic Material>Hygroscopic Swelling
Ribbon
Physics tab with Linear Elastic Material or Layered Linear Elastic Material node selected in the model tree:
Attributes>Hygroscopic Swelling