Improving the Effectiveness of Frictional Damping by Varying the Normal Load in a System with One Degree of Freedom

The primary objective of this paper is to improve the effectiveness of frictional damping in reducing the amplitude of oscillations of a single-degree-of-freedom spring-mass-damper system under external excitation. A simple Coulomb friction model is used for the analysis. To increase the efficiency of the frictional damping, a second spring is used to vary the normal load and hence the friction force. This inclination results in the coupling of geometric nonlinearities with friction factors in the system’s governing equation. This geometric nonlinearity alone (without friction) results in multiple solutions and a jump phenomenon. Coupling this geometric nonlinearity with friction force nullifies this jump phenomenon and a further reduction in amplitude. The system’s natural frequency is minimum when the second spring is positioned normally to the steady state’s direction of motion (zero inclination at equilibrium). The amplitude reduction beyond the natural frequency is much greater for this normal spring compared to an inclined spring position. The situation is different when the excitation frequency is lower than the natural frequency.