Free vibration analysis of pre-twisted rotating dovetailed blade under the flexible connection with macro-micro rough contact topography

The dynamic characteristic of the dovetailed blade plays a key role in the performance and service life of the whole aero-engine. Due to the current manufacturing accuracy and process, the macro-micro contact topography is random and various, which causes the change of the contact response in the blade root as well as the vibration of the blade body. In this paper, a new dynamic model of the pre-twisted rotating dovetailed blade under the flexible connection is established to investigate the free vibration of the blade with macro-micro rough contact topography. First, the elastic boundary of the blade root is quantified by the connection stiffness deduced from the rough contact theory. The governing equation of the blade is formulated by the thin shell theory, and the orthogonal polynomials are employed as the admissible displacement function to calculate the natural frequency though the Ritz method. Then, the effectiveness of the proposed model is validated by comparing it with the theoretical and experimental data. Finally, the influences of the pre-twisted angle, the rotational speed, the macroscopic geometrical deviation, and microscopic topography parameters on free vibration of the blades are investigated in detail. The results show that the natural frequencies have the crossover phenomenon as the parameters vary. The macro-micro topography parameters of the contact interface have a stronger ability to influence the frequency when the rotating speed is low than the high rotating speed. The presented work builds a bridge between the vibration characteristic of the blade body and the macro-micro rough contact topography of the dovetailed joint, which is very meaningful to guide the design of the aero-engine.