Add a Crack Closure subnode under a Crack node to include contact conditions between crack faces. These includes contact in the normal direction of the crack faces, and, optionally, friction in the tangential directions. Only a single Crack Closure subnode can be added per Crack node.

The Crack Closure node is only available with some COMSOL products (see www.comsol.com/products/specifications/).

Enter an expression for the Penalty factor, pn. The default expression, (2*<phys>.Eequ)/h, estimates the penalty factor from the stiffness of the adjacent domains and the mesh element size. The constant can be modified to improve accuracy or stability of the model — a too high penalty factor can lead to ill-conditioned matrices.

Select a Friction model — None, Coulomb, or User defined. By selecting None, frictionless contact is considered.

When Coulomb is selected, the critical contact friction force is a function of the contact pressure. Enter values for:

When User defined is selected, enter an expression for the Critical friction force, Tt,crit, that may depend on any quantity in the model. This expression defines the limit between sticking and sliding friction. Note, that the implementation of the friction model is only correct if Tt,crit does not depend on the current friction force.

If either Coulomb or User defined, select Compute frictional dissipation to compute and store to the energy dissipated by friction.

Physics tab with Crack node selected in the model tree: