ANALYSIS OF FREE VIBRATION OF ROTATING DISK –BLADE COUPLED SYSTEMS BY USING ARTIFICIAL SPRINGS AND ORTHOGONAL POLYNOMIALS

Abstract The free vibration of a disk –blade coupled system is investigated by the Ritz method. The boundary conditions and continuity conditions of the disk and blades are satisfied by introducing artificial springs at their joints. The orthogonal polynomials generated by the Gram –Schmidt process are used as the admissible functions. With this approach, the matrix derived from kinetic energies becomes diagonal, and the numerical calculation can become easy and stable. The mode shapes of the disk –blade coupled vibration are comprised of specific circumferential wave components which depend upon the total number of the blades and thus the modes can be classified into several types. The frequency parameters and mode shapes are obtained to investigate the vibration of the disk –blade coupled system. Some of the results are compared with the FEM solutions, and the computational efficiency of the present approach is clearly shown.