Add a Wear subnode to model mechanical wear created when the contacting surfaces are sliding along each other. Typically, the wear rate is a function of the contact pressure and the slip velocity.

The selection of the Wear node is the same as that of its parent Contact node. If significant wear can be expected on both surfaces in a contact pair, you can add two Wear nodes.

As wear involves a rate equation, it is only possible to compute wear in time-dependent studies. For other study types, the Wear node is ignored.

The Wear node is only available with some COMSOL products (see https://www.comsol.com/products/specifications/).

Select a Formulation — Deformed geometry or Offset-based. When Deformed geometry is selected, the geometry of the domain is actually changed, and a set of extra degrees of freedom are added to the model. For the Offset-based formulation, the computed wear depth hwear is added as an offset to the contact condition.

Select a Wear model — Generalized Archard or User defined.

For Generalized Archard, enter a Wear constant, kwear, a Reference contact pressure, Tn,ref, and an Exponent, n. The wear rate is defined as

Here, Tn is the contact pressure, and vslip is the slip velocity. For a classical Archard equation, n = 1. The reference contact pressure, Tn,ref, can be chosen arbitrarily, and is used only to obtain consistent units. In most cases, Tn,ref, should be chosen as the unit pressure in the current unit system (for example, 1 Pa).

For User defined, enter an expression for the general source term, f, which defines the wear rate. The default is an expression similar to 
(1e-9[m^2/N]*solid.cnt1.wear1.Tn)*solid.cnt1.wear1.vslipnorm.
This expression provides the names of the local variables for contact pressure and slip velocity, inserted in a classical Archard equation.

Finally, select a Wear surface — Destination or Source. If both surfaces in the contact pair are subject to wear, use two separate Wear nodes.

This section is only available when Formulation is set to Deformed geometry.

Choose how to set the Deforming domain selection — Automatic or Manual. When Automatic is selected, the deforming domains are assumed to be all domains adjacent to the destination or source boundaries, as selected by Wear surface. This is the default. By selecting Manual, a new section, Deforming Domain Selection, is displayed. There, you can make a manual selection of the domains to act as deforming.

In order for the mesh smoothing in the deforming domain to work properly, the mesh on all exterior boundaries, except the wear surface, should be free to slide in the tangential directions. Choose how to set the Sliding boundary selection — Automatic or Manual. When Automatic is selected, a sliding boundary condition added to all exterior boundaries of the deforming domain, expect the wear surface. This is the default. By selecting Manual, a new section, Sliding Boundary Selection, is displayed. There, you can make a manual selection of the sliding boundaries. The selection on which wear is applied is always excluded.

The remaining settings in the section affect the detailed mathematical model used for remapping the mesh in the deforming domain. For details, see Deforming Domain.

This section is present when Formulation is set to Offset-based, or when the Wear node is used in the Shell or Membrane interfaces.

Select a Shape function type — From physics, Discontinuous Lagrange, or Gauss point data. When selecting From physics, the additional thickness field is approximated by the same shape functions that are used for the dependent variables of the physics.

Physics tab with Contact selected in the Model Builder tree: