Aiming at the problem of crack monitoring of low-speed moving blades of turbine equipment such as mine ventilators, this paper proposes a crack identification method based on tip timing and tip deflection. By constructing the aerodynamic load-cantilever beam coupling model, the relationship between the tip offset and the crack length and position was quantified, and the validity of the theoretical model was verified in combination with the finite element simulation. Finally, a low-speed rotating blade test bench was built. Blades with different fault parameters were replaced under different working conditions. The tip pulse collection was completed by using the vortex sensor, achieving high-precision measurement of the tip offset. The experimental results show that the root crack of the leaf has the most significant influence on the tip offset (contribution rate 78.3%), and the offset shows a quadratic growth characteristic with the rotational speed. Within the range of 500-3000 RPM, the measurement accuracy of this method reaches ±1.5 μm, and the relative error between the experimental and simulation results is less than 5.8%, providing an effective solution for the online monitoring of cracks in low-speed moving blades.

Finite element,Blade tip timing,Blade crack