Analysis of Bending-Torsion Coupling Vibration of a Rotating Cantilever Blade

In this paper, we analyzed the coupled bending and torsional vibration of a rotating cantilever blade using the new finite element method for beams FEMB. In this method, the Timoshenko beam theory and the finite element method FEM are combined to have a more compact and accurate analytical model. Also, the six degrees of freedom DOFs of the beam element motion are considered by applying the three Euler angles sequence. Indeed, this method has the advantage of showing the centrifugal and gyroscopic coupling terms in the governing equations. The studied blade is made of aluminum alloy and is modeled by a rectangular, twisted and tapered beam. The numerical simulation of its dynamic response to a step-bending load shows rapid and persistent torsion beating that can cause premature material fatigue. Because undamped material of the blade the natural frequencies are not influenced by the gyroscopic effect. However, they are weakly affected by the centrifugal stiffness.