ANALYSIS AND COMPARISON BETWEEN A CONVENTIONAL METAL AND A METAL-COMPOSITE MARINE PROPELLER SHAFT

Abstract

The basic principal of a ship propulsion is the reactive (thrust) force generated by the propellers against the stream of water which forces the ship to propel in the opposite direction. The Shafting system is thus required to transmit the necessary torque to the propeller at a certain speed. Studies have suggested that shafts are the most common reason of failures among the whole marine propulsion system comprising of the main engine and propeller apart from the shaft. Stress concentration and torsional vibrations are the two major causes of failure in the propulsion shafting systems based on the case study of existing data. Other minor causes of shaft failures can be crack propagation in shaft line assembly, wear, corrosion, overload conditions, and material imperfections in the shaft. In comparison to Metals or Alloys, Composite materials have a high strength to weight ratio along with a high impact strength. Also, composites show a better fatigue resistance than most of the metals. By arranging the fibers in multiple directions using different orientations, the effect of stress and vibrations can be dampened. The overall aim of this paper is to analyze a Metal-Composite shaft for marine propulsion system which shows better behavior under various stress conditions as compared to the conventional metal/alloy shaft. A combination of metal and composite material in shafting system results in lower stresses and reduced torsional vibrations as compared to the existing metal shafts whereas the deformation over a longer period is also reduced. Moreover, the presence of composites in the shaft also provides superior thermal stability. The comparisons were done between the Conventional Metal shaft and the Metal-composite shaft under similar loading conditions using ANSYS Workbench for the simulation and results whereas the modelling was done using solid works 2017.