Abstract: Aircraft engine blade is one of the important parts of an aircraft engine, but it usually leads to fracture failure due to the resonance. Traditional vibration characteristic analysis for aircraft engine blades is generally based on the zero-order approximation coupling dynamics model, this model ignores the dynamic stiffening items, consequently its result has certain limitations. To analyze the vibration characteristics of the high-speed rotating blade of aircraft engines more accurately, the rigid-flexible coupling dynamics of the blade is studied. The blade is modeled as a flexible thin plate, and its off-plane deformation and in-plane deformation are all considered. Moreover the nonlinear geometric deformation, also known as the in-plane shortening caused by the off-plane deformation, is also included in the dynamic modeling, which will bring the so called dynamic stiffening effects. The approach of assumed modes is used to describe the deformation of the blade, and Lagrange dynamic equation is employed to derive the first-order approximation coupling model for the flexible blade undergoing three dimensional large overall motion. The commercial software MSC. ADAMS for the dynamic simulation of multi-body systems is also used to compute the dynamic characteristic of a rotating blade, and its results are compared with the results obtained using the first-order dynamic model established. The comparison results show that the first-order approximation coupling model’s results are accordant with the actual results, but there exist defects in results of dynamic simulation for the flexible blade at high speed with ADAMS and the zero-order approximation coupling model. Finally based on the first approximation coupling model of the flexible blade obtained, the blade’s vibration frequency, frequency veering and mode shifting are also predicted, and the feasibility of the theory and method proposed is shown.

Key words: aero-engine blades, first-order approximation coupling model, rigid-flexible coupling, zero-order approximation coupling model