Stabilization
It is common that parts in an assembly are initially unconstrained before contact forces are established in stationary and quasistatic simulations. Add a Stabilization subnode to suppress rigid body motion related to such unconstrained parts.
Quasistatic Stabilization
The stabilizing forces can be applied to different geometric entities as selected in Apply to Adjacent domains, Contact boundaries, or Contact pairs. The available options depend on the physics interface.
For Adjacent domains and Contact boundaries, the stabilization works by connecting springs to ground for those geometric entities. When Contact pairs is select, springs are instead added between the source and destination of the contact pairs of the parent Contact node.
COMSOL Multiphysics makes an estimation of the spring stiffness k required to stabilize the contact problem. If this estimate of the stiffness is too small or large, enter a new value for the Stiffness multiplier fstb.
It is essential that the stabilization forces are relaxed once contact forces are established in order not to pollute the final results of the solution. Select a MethodAutomatic or Manual, for how to relax the stabilization forces.
When the Automatic method is used COMSOL Multiphysics identifies when the contact pair(s) first comes in contact. The stabilization forces will then remain for a sufficient number of nonlinear iterations for contact forces to stabilize all adjacent parts after contact is established.
For the Manual method select Active forFirst iteration, First step, Specified number of steps, or User-defined condition, to control how the stabilization forces are relaxed.
First iteration applies the stabilization forces for the first iteration of the nonlinear solver only. This can be useful if parts are initially in contact but require friction to be constrained.
First step applies the stabilization forces for the first parameter step or time step. Enable Iteration relaxation to relax the spring stiffness with each iteration of the nonlinear solver.
For Specified number of steps, enter the number of parameter steps or time steps for which the stabilization forces are active. By enabling the Step relaxation, the spring stiffness is reduced with each step number. If Iteration relaxation is enabled, the spring stiffness is relaxed with each nonlinear iteration of the final specified step number.
For User-defined condition, enter a Boolean expression. When evaluated to true, the stabilization forces are active. This option can be useful to control the activation based on a specific parameter value in a continuation sweep, or at a specific time in a time-dependent solver.
To monitor the stabilization energy added, add a Global Variable Probe of the variable <phys>.<contact_feature>.Wstb, and output probe values while solving in the Fully Coupled or Segregated solver. This setting allows you to track how stabilization relaxes with the nonlinear iterations.
Location in User Interface
Context Menus
Ribbon
Physics tab with Contact selected in the Model Builder tree: