Abstract: The multispan rotor system(H858 compressor) is studied. The natural frequencies are obtained in the condition of bending vibration using finite element software (MSC.Patran&Nastran). With the criterion that the absolute value of the difference between the natural frequency and forcing frequency, the failure mode are defined, then the equations of the frequency reliability and the related frequency reliability sensitivity with respect to mean values and variances are mathematically expressed. And then the reliability-based robust design of structure is studied based on the reliability-based optimization model, and the numerical method of frequency reliability-based robust design is proposed. The frequency reliability sensitivity and reliability-based robust design for the multispan rotor system are extensively discussed by the above mentioned theory, which provide more theoretic evidence for the rotor system design in practical operation.

Key words: Frequency reliability, Robust, Rotor system, Sensitivity