In Plane and Transverse Eigenmodes of High Speed Rotating Composite Disks

Abstract

We apply Hamilton's principle and model the coupled inplane and transverse vibrations of highspeed spinning disks, which are fiberreinforced circumferentially. We search for eigenmodes in the linear regime using a collocation scheme, and compare the mode shapes of composite and isotropic disks. As the azimuthal wavenumber varies, the radial nodes of inplane waves are remarkably displaced in isotropic disks while they resist such displacements in composite disks. The reverse of this phenomenon happens for transversal waves and the radial nodes move toward the outer disk edge as the azimuthal wavenumber is increased in composite disks. This result is in accordance with the predictions of Nowinski's theory, and therefore, it is independent of the magnitude of the spinning velocity and the mode frequency. Although there are notable differences between the form of governing equations derived from Hamilton's principle and Nowinski's theory, transverse eigenmodes differ a little in the two approaches. We argue that the application of orthotropic composites as the core material of the next generation of hard disk drives, together with an angular velocity controller, can enhance the data access rate.