Dynamic Characteristic Analysis of Rotating Blade with Transverse Crack-Part I: Modeling, Modification, and Validation

This study aims at the systematical improvement and comparative analysis of analytical crack models for the rotating blade. Part I of this study focuses on analytical modeling, model modification, and model validation of transverse crack for the rotating blade. The most widely applied analytical crack models for the rotating blade are reviewed and compared, and then their limitations are discussed. It is indicated that the conventional analytical crack models suffer from low physical interpretability and vibration prediction accuracy. By considering these limitations of conventional analytical crack models, model modification is performed to enhance the physical meaning and improve the accuracy. First, the stress-based breathing crack model is modified by direct calculation of the breathing function based on the theory of linear elastic fracture mechanics and resetting the correction factor of centrifugal stiffening stiffness. Second, the vibration-based breathing crack models, including bilinear breathing crack model and cosine breathing crack model, are modified by introducing the coupling effect between bending stress and centrifugal stress based on the stress state at the blade crack section. The additional bending moment induced by the blade part outside the crack section is considered in all analytical models. The modified crack models' validity is verified by comparing vibration responses obtained by the modified crack models, the finite element contact crack model, and the conventional crack models. The comparative results suggest that the modified models promote the physical interpretability and improve the vibration prediction accuracy of analytical crack models.