Whirling and Vibration of Rotating Machinery Critical Speeds and Modes

Abstract

The paper investigate the vibration of the rotating shafts and whirling were theoretically by dealing with only the shaft bending without torsion. It is shown that the shaft whirling result from vibration consider for this particular system will have critical whirling speed which increases as the inertia forces of the rotor. Whirling is associated with fast-rotating shafts. When a shaft rotates it is subjected to radial or centrifugal forces, which cause the shaft to deflect from its rest position.These centrifugal forces are unavoidable, since material inhomogeneities and assembly difficulties ensure that the center of gravity of the shaft or its attached masses cannot coincide with the axis of rotation. The centrifugal forces involved and determined that the only destabilizing or restoring force was that due to the elastic properties or stiffness of the shaft. Hence, to deduce the critical speed caused an infinite deflection of shaft due to whirling. Loading response analysis can simulate the response of the rotor using Ansys program, which can help to identify the main modal frequency. To a rotating shaft, the modal analysis can give a serial of Eigen frequency, but only some of them are just the right modal frequency value we need. The harmonic analysis can extract the eigenvector of the modal analysis result, integrate them together, and show the amplitude frequency response, deformation and stress distribution characteristics of some special place of the rotating shaft