Piezoelectric-Based Vibration Reduction of Turbomachinery Bladed Disks via Resonance Frequency Detuning

Piezoelectrie-based resonance frequency detuning can alleviate unwanted vibration of turbomachinery blades, thus reducing the dangers of high-cycle fatigue while also decreasing the blade weight. This semiactive approach applies to structures that are subjected to frequency-sweep excitation and involves altering the structural stiffness (here, by switching the piezoelectric electrical boundary conditions) to avoid a resonant condition, thus limiting the blade response. Detuning requires two switches per resonance/excitation frequency crossing, including a switch back to the original the original state, many fewer than other semiactive approaches that require four switches per cycle of vibration. Resonance frequency detuning applies to any mode of vibration with a positive electromechanical coupling coefficient, and it provides the greatest normalized vibration reduction for slow sweeps, low damping, and high coupling coefficient. Yet even for a moderate sweep rate alpha = 10(-4) and modal damping zeta = 0.1%, optimally detuning a structure with an electromechanical coupling coefficient k(2) = 10% provides the same vibration reduction as increasing either the sweep rate or modal damping by an order of magnitude. With a lower sweep rate alpha = 10(-5) and modal damping zeta = 0.01%, detuning with a coupling coefficient of only k(2) = 3% provides equivalent vibration reduction as an order of magnitude increase in sweep rate or modal damping.