Validation of a Turbine Blade Component Test With Frictional Contacts by Phase-Locked-Loop and Force-Controlled Measurements

Abstract

In this paper, a validation approach for a turbine blade component test with frictional contacts is presented. The investigated system is derived from a high cycle fatigue test setup, where a turbine blade is base-excited in the clamped blade foot. The setup has been extended by laser scanning vibrometry, a force measurement platform, and feedback-controllers for both force level and phase. At first, a conventional validation of a linearized model of the system is performed at low amplitudes to ensure the correct modal basis for model reduction. After that, the nonlinear behavior around the fundamental mode is analyzed in detail. Frequency responses for different excitation levels and backbone curves are measured and assessed regarding repeatability and robustness of the measurement chain. Among other effects, overhanging branches of the frequency response were encountered. Nonlinear, amplitude-dependent modal frequencies and damping ratios are identified from the backbone curves. These data form the validation basis for a reduced-order model of the system considering nonlinear friction in the blade foot. The correlation of measurement and simulation is investigated and advantages and shortcomings of the different validation metrics are discussed.