The simulation of a full-field vibration measurement of cylindrical structures using a continuous scanning LDV technique

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The reliance of the aerospace industry on finite element models during the design of new products requires the best possible models for the prediction of the dynamic behaviour. A major aim of current experimental research is to provide a more complete set of data from a single test in a reduced amount of time, so as to increase the overall efficiency of the Finite Element updating process. To this end, a new continuously-scanning laser Doppler vibrometery measurement technique for cylindrical structures was introduced recently which allows the measurement of the dynamic behaviour of a cylindrical structure with a so-far unachieved spatial resolution in a much shorter time than with conventional measurement techniques. The new measurement system consists of several distinct parts and, as a results, shows therefore a high sensitivity towards the measurement setup. To estimate the influence of each part of the setup on the measurement results, a simulation of the measurement system will be presented in this paper. The aim of the simulation is to gain a better understanding of the sensitivity of different components and parameters to the overall quality of the measurement data. The investigation uses a sensitivity analysis of the critical parameters to weight their influence on the accuracy of the measurement and provides a procedure, based on the modal assurance criterion (MAC), to optimize the alignment parameters for a specified accuracy of the system. The results of the analysis for an aero engine casing component highlight the strong influence of the alignment parameters on the overall measurement accuracy of the ‘Lighthouse’ system but also shows the high accuracy that can be achieved with such a measurement system.