Finite element study on piezoelectric sensors for blade vibration measurements

The output of piezoelectric sensors is studied numerically as a method for monitoring the vibrations of blades used in turbomachinery. Two thick piezoelectric layers are bonded on the bottom and top surfaces of a blade at the root between the blade and the disk. The placement of piezoelectric sensors at the root allows measuring and/or computing the blade vibrations from the root without exposing the sensors to fast rotation and corrosive environment. As a preliminary investigation, the blade is modeled as a cantilever beam mounted with two piezoelectric layers at its root. The beam and piezoelectric layers are analyzed with the finite element method. The beam is excited by step and sinusoidal forces acting upward at its free end. The numerical results indicate the effectiveness of placing piezoelectric sensors at a blade root for measuring the blade vibrations.