# Sliding ContactΒΆ

The sliding contact is a special type of contact which allows dispacement tangential to the contact surface but no relative movement along the normal direction. This type of contact constraint is used to simulate sliding movement in the assembly. The two sufaces that are in contact are classified as master and slave. Every node in slave surface(slave nodes) is tied to a node in the master surface(master node) by a constraint.

For implementing a sliding contact,click on the Contacts and then Add Contact Constraint condition to create a new contact constraint. You can now assign the faces or sets that should be tied together via the assignment boxes. For numerical purposes you have to choose one of these selections as master and the other one as slave. During the calculation, the degrees of freedom of slave nodes are constrained to the master surface while only allowing the tangential movement.

Master surface for sliding contact

Slave surface for sliding contact

The settings for sliding contact varies on the type of solver used.

If you are using CalculiX,you can define a position tolerance manually or use the automatic setting. If position tolerance is used, then only the slave nodes under this tolerance will come in to contact with the master surface nodes. If the distance between a node of the slave surface and the adjacent surface element of the master surface is greater than the given tolerance, it is assumed that the node does not belong to contact definition and therefore, the degrees of freedom attached to this node will not be restricted to the master surface during the calculation. When set to Automatic, the solver will automatically set the tolerance to 2.5% of the typical element size.

If you are using Code_Aster,you can define position tolerance manually or set it to Off. When tolerance is set to Off, all the slave nodes will be tied to the master surface whatsoever. Therefore, if the larger surface is used as a master surface, one master node will be tied to multiple slave nodes leading to artificial stiffness in the slave surface.

Note

1. You should be very careful while assigning a surface as slave or master. If a larger surface is chosen as slave (or surface with higher mesh density),the computation time will increase significantly and it might also result in wrong solution, especially when no specific tolerance criteria is provided. 2. This is a linear constraint type, therefore, no large sliding and rotations are allowed in the proximity of a sliding contact.