Friction
Use the Friction subnode to model friction losses in the joint.
The Friction subnode can be added to the Prismatic Joint, Hinge Joint, Cylindrical Joint, Screw Joint, Planar Joint, and Ball Joint.
Friction
Enter a Frictional coefficient μ.
Enter a Characteristic slip velocity v0. The default is mbd.diag*(1e-3[1/s]), where the mbd.diag variable contains the diagonal of the bounding box of the geometry. The characteristic slip velocity should be small when compared to actual velocities in the joint. It is the velocity with which the joint slides even under sticking conditions.
For the Hinge Joint, enter a Hinge radius r.
For the Cylindrical Joint, enter a Cylinder radius r.
For the Screw Joint, enter a Screw radius r.
For the Ball Joint, enter a Ball radius r.
The radius is used for computing the friction moment in the joints that have a rotational degree of freedom.
For the Planar Joint, select a Friction modelTotal force at center of joint or Distributed force on selected boundaries. By distributing the friction forces, it is possible to obtain a moment caused by friction for a rotational relative motion. When Distributed force on selected boundaries is selected, a Contact Area subnode is added by default. In that subnode you make the selection of the boundaries on which the friction forces should be distributed.
Normal Force
In this section you supply details about how to compute the force acting on the joint, to which the friction loss is proportional.
The Contribution from joint forces check box is selected by default, which implies that the friction forces are computed based on normal forces determined from the forces acting the joint. If you click to clear the check box the friction force is independent of the forces acting on the joint, and the following parameter selection is not required.
Select an option from the Normal force defined through list — Attachment reaction forces, Joint forces and moments, or for the Prismatic Joint, Joint force in specified direction.
For the Ball Joint, no further selection is required.
The alternative Attachment reaction forces is not available if the joint is attached to a rigid domain or to an attachment in a Shell or Beam interface.
For Joint forces and moments enter values for the Joint moment contribution factors αl1 (for the Prismatic Joint only), αl2, and αl3.
For the Prismatic Joint, and if Joint force in specified direction is selected, enter values for each space coordinate for the Direction of surface normal en0.
By selecting Contribution from interference fit check box you can define the normal forces by pressure or total force from an assumed interference fit.
Select an option from the Normal force defined through list — Pressure or Total force.
For Pressure enter a value for p. Also enter a Contact area A.
For Total force enter a value for Fn.
Advanced
Enter values or expressions for the:
Maximum friction force Ff,max. The default is Inf, which means that no upper limit is imposed on the friction force.
Location in User Interface
Context Menus
Multibody Dynamics>Prismatic Joint>Friction
Multibody Dynamics>Hinge Joint>Friction
Multibody Dynamics>Cylindrical Joint>Friction
Multibody Dynamics>Screw Joint>Friction
Multibody Dynamics>Planar Joint>Friction
Multibody Dynamics>Ball Joint>Friction
Ribbon
Physics tab with Prismatic Joint, Hinge Joint, Cylindrical Joint, Screw Joint, Planar Joint, or Ball Joint selected in the model tree:
Attributes>Friction