Friction and impacts during oscillations lead to discontinuities of the velocity and of the internal forces in the time-domain and to changes in the number of degrees of freedom, Ibrahim (1994). The analytical procedure for the integration of such non-smooth motions is to compute the history dependent separation times and to patch together a sequence of solutions for successive smooth problems, Popp (1998). However, this very accurate procedure has limits even for a relatively low number of generalized coordinates because of the required computational effort. Regularization techniques as usually used with FE allow to avoid the exact computation of all discontinuities by smoothing. But there is a big uncertainty in the choice of the regularization parameters needed for a sufficiently correct description of the oscillations under investigation. Stationary solutions of two forced mass-spring oscillators are used to calibrate the regularization parameters by comparing analytical results with regularized ones. This allows to compute the self-excitation of a continuous system and to prove the phenomena with known experimental data.