Damping in piping systems due to local nonlinearities

In the past the influence of nonlinearities towards the dynamic behaviour of systems was pointed out by a large number of investigations. Especially in the field of piping systems several projects were conducted. One common way to reduce the data gained by experiments is to determine equivalent damping values which take into account the energy dissipation of local nonlinearities. Different methods for instance ‘log-decrement-method’, ‘half-power-method’, ‘canbe-fit-method’ are frequently used. If one compares the damping values which were determined by using experimental data an extreme scattering can be observed (1) even if one tries to find correlation between damping and stress or frequency. This paper will show how local nonlinearities contribute to the overall behaviour by using analytical results. The investigations cover simple multi-degree-of-freedom systems as well as typical NPP-piping.