On dry friction modelling and simulation in kinematically excited oscillatory systems

This paper deals with the analysis and simulation of a general single degree of freedom (sdof) oscillatory system with idealised linear viscous damper and dry friction. For dry friction modelling the phenomenological macro-slip approach is employed, described in mathematical form either by the signum function approach or by the physically correct stick–slip approach assuming switching phenomena on a short time scale. Both approaches are illustrated first using a steady-state harmonic acceleration excitation with constant amplitude and then a stationary random acceleration excitation, corresponding to a field-measured excitation in a vehicle. The differences in the two approaches are highlighted, indicating that the physically correct stick–slip approach describes the friction phenomenon better than the standard signum approach. The signum approach is prone to false numerical oscillations completely distorting the acceleration response signal in comparison to measured suspension system response. The acceleration transmissibility response is analysed in respect to the dry friction force magnitude, employing stationary random excitation. A sdof oscillatory system without viscous damping, subjected to both stationary random acceleration and harmonic acceleration is analysed, too. It is shown that such a system can be used without serious practical problems; however, no implications on its performance from the analysis under harmonic constant amplitude acceleration excitation can be made.