Simulation and Identification of Multi-parameter Cracks of High-speed Rotating Blades

The blade vibration has always been one of the main factors that restrict the improvement of turbomachinery performance such as aero-engines. The cracks caused by resonance are very common under the harsh working environment. This paper studies the effect of cracks parameters on the vibration characteristics by the finite element analysis. Through the finite element calculation, when there is a crack, the frequency decreases very rapidly, and the frequency declines with the extension of the crack, and the decreasing trend increases gradually, but the frequency is not sensitive to the width. As a nonintrusive vibration measurement method, blade tip timing (BTT) technology has the potential to replace strain gauges for blade dynamic stress monitoring, experimental verifications are carried out on a twisted three dimensional blade test bench. The deviation resonance frequency of blade with 3 mm cracked is 0.2% between the finite element calculation and experimental verification. The first order natural frequency of the blade is significantly affected by the crack which is at root. The cracks will lead to the disk mistuning, which causes frequency changes on the healthy blade.