Force Frictional Sliding contact is not designed to model a sticking situation. It works well for sliding contact where the friction leads to a resisting force (opposed to the sliding velocity) which is directly proportional to the normal contact force Ft=mu*Fn. In order to avoid integration difficulty with low sliding velocities (basically when the contact would ideally be sticking or close to sticking), the friction factor varies linearly between 0 and its nominal values if the sliding velocity is lower than a given velocity.
In summary,
If ||v||>=v_tol, Ft=mu*Fn
If ||v||This velocity tolerance is internally computed from the contact radius among many other parameters. Unfortunately, this tolerance cannot be obtained or set by the user. However, there is a command that affects its computation:
options=CS_SolverOptions()
options.VelocityToleranceFactor=1.0
The default value is 100. It allows to improve the behavior to be “closer” to a sticking contact but it won’t ever be perfectly sticking. With a factor=1 (a lower velocity tolerance), it will be possible to have lower sliding velocities, like an “almost sticking” contact status.