Abstract
The natural vibrating behavior of a linearly pre-twisted windmill blade of composite cross section is investigated using finite element analysis. Application of three dimensional beam theory embedded in the Hamilton's principle of dynamics leads to equations of motion of an element. The consistent mass matrix, linear stiffness matrix, inertial damping matrix, stiffness matrix due to frame rotation, and geometric stiffening stiffness matrix due to tension preload (centrifugal forces) are derived. A structural module for analysis of the fundamental vibration of a beam is then developed to obtain the various vibrating modes of blades under rotating conditions. A number of total pre-twist angles, blade root angles, blade rotating speed, and radii of hub are assumed so that effects of such parameters on the natural frequencies of the rotating blades may be realized.
Published Version
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