Measurement and Evaluation of Interface Forces During Base-Driven Tests.

This paper first summarises analytical equations which govern the dynamic behaviour of elastomechanical structures under base excitation. Special attention is focused on the dynamics at the interface between the vibration table and test structure. The dynamic relations at the interface are explained with particular consideration to the interface forces. An example of an interface forcing function is shown and discussed. A suitable device for force measurements (FMD) is described. It was specifically designed for themeasurement of the six dynamic interface forces and moments between a shaker table and a tested structure. The FMD was recently utilised for base-driven tests on a liquid propellant tank and support structure. The test set-up and the performance of the dynamic tests are described. During the tests the interface forces, the base accelerations, and the structural responses were recorded. Based on the measured data, a modal analysis is performed and results are given as an example. The identification of effective and modal massesfrom the measured interface forces is demonstrated and exemplary results are discussed