Using the Friction subnode, you can add friction to a Contact node.

The selection of the Friction node is the same as that of its parent Contact node. If you add more than one Friction node under the same parent, the last one will override all the preceding nodes. If Friction and Adhesion are present under the same Contact node, the friction settings will be ignored once the adhesion criterion is fulfilled.

Select a Friction model — Static Coulomb friction or Exponential dynamic Coulomb friction. The latter can only be used in a time dependent analysis, since the value of the frictional coefficient depends on the slip velocity. Enter the following data:

Select the algorithm used for computing the tangential forces and sliding criteria, Augmented Lagrangian or Penalty. The method can be selected independently of the corresponding Contact Pressure Method setting in the parent Contact node.

If Tangential Force Method is Augmented Lagrangian, select the type of Penalty factor control — From parent (default), Preset, Manual tuning, or User defined. The settings give access to an increasing level of detailed control of the penalty factor for the sliding.

In the default case the settings are taken from the Contact node to which the current Friction node is a child. For a description of the settings, see the documentation of Penalty Factor under Contact. The only difference is that the default value of the User defined penalty factor is min(1e-3*5^niterCMP,1)*solid.<contact_tag>.E_char/3/solid.hmin_dst.

If Tangential Force Method is Penalty, select the type of Penalty factor control — From parent or User defined. The choice From parent is only available if Contact Pressure Method is set to Penalty in the parent Contact node. In that case, the settings are taken from the Contact node to which the current Friction node is a child. When User defined is selected, enter Tangential pressure force factor pt. The default value is solid.<contact_tag>.E_char/3/solid.hmin_dst.

If Tangential Force Method is Augmented Lagrangian, enter values or expressions for the components of the initial force acting on the destination surface as Friction force Tt.

To determine whether friction effects are active when starting the solution or not, select the Previous contact state — Not in contact (the default) or In contact.

For In contact enter values or expressions for the Previous mapped source coordinates xm, old. These serve as initial values to compute the tangential slip. The default value is (X, Y, Z) and indicates that the contacting boundaries are perfectly coincident in the initial state. The mapped source coordinates are defined as the location on the source boundary where it is hit by a certain point on the destination boundary.

This section can only be displayed if Tangential Force Method is Augmented Lagrangian. To display it, click the Show button () and select Discretization. Select a shape-function order for Friction force — Linear (the default), Quadratic, Cubic, Quartic, or (in 2D) Quintic. This setting should usually not be changed. Selecting anything else than Linear requires that the solver sequence is modified manually because the lumped solver is then no longer optimal for the update of the tangential forces.

To display this section, click the Show button () and select Advanced Physics Options.

For numerical reasons, the gap value will not be exactly zero even when the boundaries are in contact. A certain small positive value of the gap must thus be used to determine that the boundaries touch each other. so that friction forces can be introduced. Select a Friction detection — Automatic or Manual. For Manual enter an absolute value for the Friction detection tolerance Δcontact, which is the gap when the friction becomes active.

You can also request that the total accumulated slip distance it stored by selecting the Store accumulated slip check-box.

 Solid Mechanics>Contact>Friction
 Multibody Dynamics>Contact>Friction

Physics tab with Contact selected in the Model Builder tree:
Atributes>Friction