Scanning LDV Measurement Technology for Vibration Fatigue Testing

Abstract

Vibration fatigue testing is a verification method for structural components. It is rapid and cost efficient, and it is often performed for aero-engine components because it replicates closely stresses under normal operation conditions. This testing methodology is well known for metallic components but it can also be applied to composites for studying failure caused by high cycle fatigue. Resonant frequency decay is usually the main parameter used to assess fatigue behaviour of metallic components at a given excitation level. However for composites this alone is not very useful and several measurement parameters need to be monitored in order to understand the behaviour and develop a set of failure criteria. Scanning LDV is an excellent measurement system which enables a variety of options thanks to its non-contact nature. This manuscript will show how this system can be used for monitoring several parameters during vibration fatigue testing. A custom made control panel called MONTEVERDI and the independent use of the scanning mirrors allow the SLDV to perform several tasks: (1) Phase Lock Loop (PLL) to excite the component always at resonance, (2) measuring of Operational Deflection Shape (ODS) using either step or continuous scanning method, (3) custom calibrated strain measurement and (4) phase portrait for nonlinear vibration analysis. This paper will present the great potential of using SLDV for performing time consuming vibration fatigue testing via an automated control panel.