Study on Compensatory Magnitude of Axial Misalignment for Flexible Couplings Assembled by Interference Fit

In general, there are three kinds of common metal flexible couplings, such as diaphragm coupling, disc coupling and gear coupling. Gear couplings, compared with diaphragm couplings and disc couplings, usually have a little ability in compensating misalignments. Diaphragm couplings have nice compensatory ability in radial, angular and axial directions, especially muti-diaphragm couplings have better compensatory ability than disc couplings. Diaphragm couplings are also suitable for higher rotating speed than disc couplings. They are high technology products, are widely used in micro gas turbine. Joint way of a diaphragm coupling with a shaft usually uses bolts and interference fit. In this article, a flexible diaphragm coupling assembled by interference fit was taken as research object. By comparing three kinds of interference assembly forms of the coupling, a most reasonable form was chosen and its axial compensatory ability was treated as main research content. An idea that “established process of balances is the varied process of misalignment magnitude” was presented. Combining the idea and the characters of interference fit, new boundary conditions were confirmed via bringing assumed shearing forces, and then the physical model was established based on the new boundary conditions mentioned above. Two-step method, based on the physical model, was presented to solve the axial compensatory magnitude. Meanwhile centrifugal stress and torsional shearing stress of diaphragms of the coupling were also considered in the process of calculation. Finally an example was done to support the method. Some important conclusions were acquired by calculating, and they are significant for design of the flexible diaphragm couplings.