Prediction of resonant response of shrouded blades with three-dimensional shroud constraint

In this paper, the three-dimensional shroud contact kinematics of a shroude d blade system is studied. The assumed blade motion has three components, n amely axial, tangential, and radial components, which result in a three dim ensional relative motion across the shroud interface. The resulting relativ e motion can be decomposed into two components. The first one is oil the co ntact plane and can induce slick-slip friction. The other component is perp endicular to the contact plane and can cause variation of the contact norma l load and, in extreme circumstances, separation of the two contacting surf aces. In order to estimate the equivalent stiffness and damping of the shro ud contact an approach is proposed. In this approach, the in-plane slip mot ion is assumed to be elliptical and is decomposed into two linear motions a long the principal major and minor axes of the ellipse. A variable normal l oad friction force model (Yang and Menq, 1996) is then applied separately t o each individual linens motion, and the equivalent stiffness and damping o f the shroud contact can be approximately estimated. With the estimated sti ffness and damping, the developed shroud contact model is applied to the pr ediction of the resonant response of a shrouded-blade system. The effects o f two different shroud constraint conditions, namely two-dimensional constr aint and three-dimensional constraint, on the resonant response of a shroud ed blade system are compared and the results are discussed.