To examine how great the difference is between a calculated and a measured value with regard to a resonant amplitude of grouped steam turbine blades, the resonant amplitude of grouped blades was calculated and measured. The turbine blades were excited by an electrical magnet. Therefore, the calculated values of the distribution of the resonant amplitude at the natural frequency nearly agreed with the measured ones. At some measuring position, a difference between the calculated values and the measured ones existed, and the measured values became about twice the calculated ones in the worst case. With regard to the direction of the vibration of the blades and the resonant stress, the calculated values nearly agreed with the measured ones. Therefore, if an exciting force during operation can be decided when designing blades, the vibration amplitude and stress of the grouped blades can be predicted by the calculation.
