Analysis of Vibration of the Turbine Blades Using Non-Intrusive Stress Measurement System

A Non-intrusive Stress Measurement (NSMS) was developed to measure coupled vibration on turbine blades. These systems can report the actual stresses seen on the blades; detect synchronous resonances that are the source of High Cycle Fatigue (HCF) in blades; measure individual blade mistuning and even help separate complicated, coupled resonances in bladed disks. Tests were successfully performed at high temperature and measured both tip timing and tip clearance of all blades. Non-Intrusive Stress Measurement Systems (NSMS) was used successfully in measuring bladed disk vibration, and was consistent over many runs. The SDOF curve fit and Circumferential Fourier fit were used to identify resonance amplitudes, resonance RPM and damping for all blades. The results of the two data-reduction methods matched well. Because tip deflection for every blade can be obtained with NSMS system, it might be possible to reduce the fatigue margin relative to the fatigue margin based upon strain gage data from a few blades.