Analysis of Slip Damping With Reference to Turbine-Blade Vibration

Abstract

Abstract Energy of vibration may be dissipated by microscopic slip-on interfaces where machine elements are joined in a press fit. In this paper slip damping is studied as an agent in reducing turbine-blade resonant stresses and prolonging turbine life. A general theory of slip damping is developed and an expression for the energy loss per cycle of oscillation is found. The predictions of the theory are compared with the results of controlled experiments. It appears that the theory is in satisfactory agreement with experiment and with measurements made on turbine blades elsewhere in this country and abroad. The implications of the general theory in the design of turbine blades are discussed. It appears that slip damping is capable of being an effective agent in reducing resonant stresses, especially in the “stall-flutter” condition where aerodynamic damping is inadequate. The design of a slip-damping joint which would achieve theoretically possible energy decrements much larger than are present in existing commercial construction is shown to depend on the maintenance of an optimum contact pressure.