[MBDyn-users] Implementation of friction models
Marco Morandini
marco.morandini at polimi.it
Tue Jan 24 12:38:19 CET 2017
> I understood the basics but I
> don't understand the need of a shape function or the average radius model
> definition.
The friction coefficient gives you a relation between the normal and
tangent components of the joint reaction force at the point of contact.
To compute the moment from the tangential reaction component you need
the joint radius.
The joint unknowns is the total reaction force, not the normal
component. Thus, the need of the shape function that for a slightly
loaded hinge is equal to f/sqrt(1.+f*f). See
ALI FARAZ and SHAHRAM PAYANDEH, Towards approximate models of Coulomb
frictional moments in: (I) revolute pin joints and (II) spherical-socket
ball joints, Journal of Engineering Mathematics 40: 283–296, 2001.
Fig. 2 and Eq. 2. You'll find there expressions for heavily loaded
joints too, but right now they are not implemented in MBDyn.
Hope this helps,
Marco
More information about the MBDyn-users
mailing list