MECHANICS OF CONTACT INTERACTION BETWEEN PROPELLER SHAFT AND STERN BEARING UNDER THE TRANSVERSE VIBRATIONS

Abstract

Objectives. In order to improve the accuracy of calculations in the design of ship shafting systems, the problem was to determine the stiffness coefficient of the stern bearing material taking into account its geometric dimensions.Methods. The contact problem of interaction between a propeller shaft incorporating a stern bearing is considered. The calculations are reduced to solving the contact problem of a beam on an elastic base, which simulates a propeller shaft and a deadwood stern bearing in the design scheme.Results. The characteristics of the mechanical and elastic properties of the Winkler base are given. Formulas are composed for determining the components of the elastic forces and deformation values. A study was carried out using a special device for determining the stiffness coefficient of samples made of caprolon. Dependency was obtained for the determination of the stern bearing stiffness coefficient, taking into account its geometric dimensions and shape. Two batches of sample inserts were made for the investigations: samples of different lengths (110, 90, 70 mm) with a thickness of 7 mm, and samples 110 mm long with various thicknesses (6-7 mm). The samples were compressed under the impact of a defined load by a test laboratory hydraulic press of P-125 type. The values of sample offset during compression were measured by an alesometer according to GOST 4651-82. The results obtained were statistically processed with a confidence level of a = 0.95. Based on the average values of the results obtained, a dependency graph of the sample compression value was plotted against the defined load for different lengths of the sample. The average value of the sample stiffness coefficient was determined in the proportional zone. A nonlinear law of sample deformation was observed during a further load increase, as evidenced by a rapid change in the length and shape of the samples.Conclusion. The proposed method for determining the stiffness coefficient of the stern bearing, taking into account its dimensions, allows the system's stiffness characteristic to be determined more accurately, and can be used in the design calculations of the ship's shaft. The reliability of the result is assured by rigorous mathematical calculations.

Keywords

• contact mechanics
• stern bearing
• stiffness coefficient
• transversal vibrations