关键词: 高速旋转叶片；叶尖定时；阻尼测定；振动响应

Abstract: Aiming at the difficulties in identifying modal damping of high-speed rotating blades，a novel method named phase tangent slope method was proposed. In the method，the tip timing technique was used to obtain vibration response of blades，and the tangent slope of phase-frequency curve at resonant point was employed to calculate modal damping ratio. After the Lagrange interpolation of the preliminary phase-frequency data，the tangent slope at resonant point was obtained through central difference. Tip timing theory was introduced，and then theory of phase tangent slope method was also presented，and it was applied in the damping identification of simulated damping and actual high-speed rotating centrifugal blades. The results demonstrated that error of the phase tangent slope method can reach up to 1×10-4 % and is significantly smaller than the maximum error 53.68 % of the half-power bandwidth method as long as the interval of frequency ratio is small enough (e.g. 1×10-6). In the modal damping identification of rotating blades，the identified results of the phase tangent slope method，the half-power bandwidth method and Hood software can be comparable in magnitude. Modal damping ratios of various blades show a certain degree of dispersion，while all the values fall within the scope of 8.0×10-4 to 1.2×10-3. It indicates that the identification results of the phase tangent slope method are reliable and credible.

Key words: High-speed rotating blade；Blade tip timing；Damping determination；Vibration response