Stein G., Zahoranský R., Múèka P.

The dry-friction influence on the properties of mechanical system is of permanent interest. The fundamental analytical treatment of this phenomenon is attributed to Den Hartog, back in 1931, using the harmonic balance method and force excitation. The proposed paper will deal with kinematically excited single DOF oscillatory system, incorporating both viscous and dry-friction vibration damping. By means of simulation the influence of the combination of viscous damping and dry-friction force on system properties will be analysed. Two different approaches will be described – one using the signum function approximation, the second one physically correct switching between slipping and sticking states. The pros and cons of both approaches in comparison to classical analytical approach will be illustrated. Real random excitation will be used for illustration of models difference. Means for optimisation of oscillatory system vibration mitigation properties will be illustrated. Simulation results will be compared to laboratory measurements. Model will be extended to include the influence of the end-stops. Reasonable agreement between simulation results and real experimental data from laboratory and field tests has been attained, which illustrates the suitability of this approach in engineering practice. The approach is of generic nature and can be used for oscillatory systems simulation analysis in other applications too. This research has been undertaken within the European project VIBSEAT (Contract No. G3RD-CT-2002-00827). The results to be presented were used in analysis and improvement of vibration isolation properties of driver’s seats subjected to real random kinematical excitation.