A Response Prediction and Optimisation of a Frictionally Damped Structure

Summary

Theoretical analysis assuming coulombic friction is, even for simple structures, lengthy in computation time. This has led to the development of an analysis using an equivalent sinusoidal force. The normal force is determined that, when applied across a frictional damper attached to a beam, minimises the displacement response at a given point over a limited excitation frequency range. The experimental and theoretical response patterns obtained are similar, and such differences that do exist can be explained by comparing the assumed and measured characteristics of the damper interface surfaces. The normal force, frictional force and coefficient of friction varied by only 5% over the first 10⁷ cycles and tended to constant values. The coefficient of friction was found to increase with the amplitude of slip of the damper interface. It is shown theoretically that the optimum response using a frictional damper is comparable with that using a viscous damper. The essential requirement of the frictional damper system is that it shall traverse the free resonant peaks in a ‘locked’ state and the clamped resonant peaks in a ‘slipping’ state.