INTL - A Strategy for the Identification and Characterization of Non-linearities within Modal Survey Testing

Kurzfassung

Modal identification tests on aircraft prototypes or spacecraft structures like satellites are mainly performed to experimentally identify the structural dynamic behaviour in terms of a modal model. This assumes linear dynamic behaviour of the structure. In practice, most of the investigated and tested structures exhibit some non-linear behaviour. In this paper the INTL (Identification of Non-linearities by Time series based Linearity plots) method which is based on the force-state mapping approach (Masri et al. [1]) is used to identify modal non-linear parameters and to characterize the non-linearity for a single mode of vibration. The method is able to identify any type of non-linear function, including discontinuous functions, even when stiffness and damping non-linearities occur together in a single mode. In the second step of the method linearity plots are created from the restoring force plot by using the Harmonic Balance method. The INTL strategy and its utilization during modal identification testing are described. The application of the method is illustrated by an example. The benefits and the limitations are discussed.