By adding the Predeformation subnode, you can prescribe that the spring force is zero at a nonzero spring extension.

Select the Spring type and its associated spring constant or force using Table 4-6 as a guide.

Use the built-in variables for the thin layer extension for the options Force per area as function of extension, Force per length as function of extension, or Total force as function of extension. The names are <item>.uelt1, <item>.uelt2, and <item>.ueln, where <item> is the name of the Thin Layer node (for example, solid.tl1), and t1, t2, and n are the coordinate names of the local boundary system.

The spring constants can be entered as Isotropic, Diagonal, or Symmetric. For Isotropic the same spring constant is used in all the diagonal elements of the spring matrix.

Enter the Mass type of the thin elastic layer — Total mass, Mass per reference volume, ρV, or Mass per reference area ρA. For thin layers on 2D geometries, it is also possible to enter the Mass per reference length ρL.

Select a Formulation — From study step, Total Lagrangian, or Geometrically linear to set the kinematics of the deformation and the definition of strain. When From study step is selected, the study step controls the kinematics and the strain definition.

When From study step is selected, a total Lagrangian formulation for large strains is used when the Include geometric nonlinearity checkbox is selected in the study step. If the checkbox is not selected, the formulation is geometrically linear, with a small strain formulation.

To have full control of the formulation, select either Total Lagrangian, or Geometrically linear. When Total Lagrangian is selected, the physics will force the Include geometric nonlinearity checkbox in all study steps.

Select a Strain decomposition — Automatic, Additive, Logarithmic, or Multiplicative to decide how the inelastic deformations are treated. This option is not available when the formulation is set to Geometrically linear.

The Strain decomposition input is only visible for material models that support both additive and multiplicative decomposition of the deformation gradient.

Select how to compute the energy dissipated by Creep, Plasticity, Viscoplasticity, or other dissipative processes.

Select how to Store dissipation — From physics interface, Individual contributions, Total, Domain ODEs (legacy), or Off.

Use From physics interface to treat the dissipative processes as specified in the settings of the physics interface, see for instance Energy Dissipation in the Solid Mechanics interface.

Use Individual contributions to treat each dissipative process independently. Selecting this option gives a more flexible implementation for problems where dissipation occurs at different time scales, and you want to distinguish each phenomenon separately.

Use Total to accumulate all the dissipative processes into one common variable.

Use Domain ODEs to accumulate the dissipative processes into ODE variables instead of internal state variables.

To display this section, click the Show More Options button () and select Advanced Physics Options in the Show More Options dialog. For more information about this section, see Constraint Settings in the COMSOL Multiphysics Reference Manual.

Physics tab with Thin Layer node selected in the model tree: