COMSOL 6.2 - Friction

Use the subnode to model friction losses in the joint.

The subnode can be added to the Prismatic Joint, Hinge Joint, Cylindrical Joint, Screw Joint, Planar Joint, and Ball Joint.


	Friction can only be applied to the joints in a time-dependent analysis.

Friction

Enter a μ.

Enter a 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.

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For the Hinge Joint, enter a r.

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For the Cylindrical Joint, enter a r.

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For the Screw Joint, enter a r.

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For the Ball Joint, enter a 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 — or . By distributing the friction forces, it is possible to obtain a moment caused by friction for a rotational relative motion. When 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.


	For a detailed discussion of the effect of the settings for the normal force for each joint type, see Theory for Friction in Joints

The 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 list — , , or for the Prismatic Joint, .


	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 enter values for the αl1 (for the Prismatic Joint only), αl2, and αl3.

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For the Prismatic Joint, and if is selected, enter values for each space coordinate for the en0.

By selecting check box, you can define the normal forces by pressure or total force from an assumed interference fit.

Select an option from the list — or .

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For enter a value for p. Also enter a A.

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For enter a value for Fn.

Advanced

Enter values or expressions for the:

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Ff,r.

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Ff,max. The default is Inf, which means that no upper limit is imposed on the friction force.


	Theory for Friction in Joints

Location in User Interface

Context Menus

Ribbon

Physics tab with , , , , , or selected in the model tree: