PASSIVE VIBRATION SUPPRESSION OF BEAMS AND BLADES USING MAGNETOMECHANICAL COATING

The feasibility of using magnetomechanical coating for enhancing high damping capacity on turbine blades is investigated. An analytical procedure is developed for modelling the dynamic behavior of beams and blades coated with a plasma-sprayed iron–chromium-based coating. The stress- or strain-dependent damping capability of the coating material is evaluated experimentally and further quantified with a distribution function proposed by Smith and Birchak (1968 Journal of Applied Physics39, 2311–2316 [1], 1969 Journal of Applied Physics40, 5174–5178 [2]). The equation of motion and associated boundary conditions are derived for uniformly coated beams. The resulting equation of motion is solved for beams using a closed-form procedure. To validate the closed-form solutions and further investigate the effects of a thin coating on high-frequency chordwise bending modes or stripe modes (the terminology widely used by the turbine engine industry) of the vibrations of a curved blade, a three-dimensional finite element approach is used, which allows one to systematically determine the stress-dependent damping properties. The finite element results show that a thin magnetomechanical coating layer can make a significant contribution to the damping and reduction of vibratory or alternating stresses at various high-frequency vibration stripe modes.