DETECTION OF NONLINEARDYNAMIC BEHAVIOUR OF MECHANICAL STRUCTURES

摘要

The aim of this paper is to emphasize nonlinear dynamic behaviour of some mechanical structures in order to illustrate that such behaviour is not only of academic importance As a consequence, the need for reliable methods to detect non-linear dynamic behaviouris expressed. The assumption of linear behaviour has to be verified to validate consistency of results of a modal analysis test. In this paper, tests on three mechanical structures are represented: checks on linearity indicated the presence of some typical nonlinear dynamic behaviour. Following structures have been tested: a longitudinal beam of a carframe, a measuring-instrument and the IGLOO-module of ESA-spacelab. These structures show a degree of nonlinearity too significant to be neglected if accurate measurements are desired. Popular methods to check linearity are Maxwell's reciprocity theorem and the superpositon principle but these are rather cumbersome techniques. Therefore the directives to develop a more practical and reliable detection method, are described.