The study of the effects on stress augmenting factors by the erosion troubles to the propeller of a vessel

While in operation, a vessel had a problem of erosion with its propeller, which have caused a default accordingly. Therefore, with the purpose to investigate the effects on stress augmenting factors by the erosion troubles in the propeller, calculations were done first to the circular eroded areas in analog test specimens by means of the 20-node hexahedron isoparametric element and the live-and-dead cell. As a result, the distribution of the maximum stress has been determined in different erosion cases, and so have been the changing rules of the stress augmenting factors according to different etch depths. That is to say, the stress augmenting factor will increase as the erosion etch pit goes deeper. Specifically speaking, when the pit is eroded approximately to the depth of 2.8mm, there will be a rapid change to the stress augmenting factor. Moreover, based on the simulated test results, a comparative study was then made on the analog test specimens in these 4 cases in terms of erosion degree: no-corrosion, 3.23%, 21.61%, and 30.41%, with appropriate stress augmenting factors obtained. Finally, a fracture criterion was applied to study the changing tendency of the allowable stress of the vessel propeller as well as the rules that the maximum allowable stress varies with the increase of fracture length, which, therefore, offers a theoretical basis for formulating a set of criteria to decide whether or not a ship propeller should be discarded as useless.