Rubbing characteristics of a rotating blade with cracks

A novel compound fault modeling (NCFM) method is proposed to provide a qualitative numerical characterization of the cracked blade with the rubbing fault. Firstly, the proposed NCFM method incorporated the effects of centrifugal stiffening and spinning softening on the rotating blade under aerodynamic force. Secondly, multiple factors including variable speed, crack depth, and multi-failures modes (i.e., crack fault, rubbing fault) are considered to establish the effect matrixes (i.e., the additional effect matrix introduced by rubbing fault and the nonlinear crack fault) of different failures. Beside, a modified rubbing force model of the cracked blade is established. Moreover, an in-depth comparative analysis of the obtained results with the variable contact friction coefficients, casing stiffness, rotational speed, and crack stiffness underlines the relevance of compound fault. On the one hand, the continuous increase of rotational speed or crack depth will intensifies rubbing, including a decrease in rubbing interval and an increase in rubbing displacement amplitude. On the other hand, crack fusion leads to earlier development of rubbing, with smaller rotational speeds corresponding to less severe rubbing.