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An analytical investigation of the squeak in the mechanical seal used in water pumps is presented in this paper. The squeak investigated in this paper is generated by self-excited torsional vibration of the rotational shaft of the water pump, and is caused by the stick-slip phenomenon of the mechanical seal. The fundamental cause is the friction characteristic of the seal. In addition to the seal friction characteristic, the effects of other parameters: shaft dimensions, rotor inertial moment and seal attachment position, have been analyzed in this paper. The simulation model was constructed using an equivalent vibration system obtained from the natural torsional mode shape of the shaft and its kinetic energy. It was confirmed that the stability of the stick-slip self-excited vibration, which generates the squeak, could be predicted using the simulation model.

This paper describes a bench test evaluation method for vibratory forces caused by a propeller shaft. Most of the vibratory forces are usually generated at the joints of a propeller shaft. They are classified as vibratory forces of axial, radial and moment directions. Axial force can be easily evaluated by measuring the load washer outputs. On the contrary, radial and moment forces can not be analyzed enough clearly even though the outputs are measured, because the load washer for both forces is the same and the outputs depend on the sum of these forces. In this paper, an algorithm for the evaluation method is described. In this method the outputs, as a sum of the forces, are by computation translated separately into kinds of forces which are generated at each joint. The translated results are calculated using an inverse matrix of influence coefficients between the forces and the outputs. Using this method, the evaluation is effective for analyzing the mechanism of the forces.