摘要：Marine Diesel engines which are to be implemented on ships supervised by a classification society shall be type approved. From the point of classification society view the most important phase of the type approval process is approval of the documentation. The essential engine element to be approved during that phase is its crankshaft from the point of dynamic durability, based upon fatigue strength. Though the procedure of crankshaft analysis has been unified by the International Association of Classification Societies (IACS) in the document IACS UR M53, the difficulty in its implementation is based upon the fact that this document lacks essential details, e. g. unified method of determination of crank forces and the stresses range. The aim of this paper is to describe the procedure developed in the Croatian Register of Shipping (CRS) implemented to determine the mentioned forces and stress ranges, starting from the pressures in cylinder, submitted by the engine manufacturer. The basic idea is the analysis of the connecting rod motion and its modelling by three concentrated masses. Implementing stress concentration factors in accordance with the present UR M53, acceptability factors are determined as a result of the fatigue strength analysis. The procedure has been illustrated on a real example of a marine four-stroke Diesel engine, which has been tested on the manufacturer’s test bed, at the beginning of 2003. The four-stroke example is chosen, because in this type of engine crankshafts are solid, i. e. not semi-built, for which additional criteria would be applicable. The conclusion gives guidelines for the further development of the specified procedure. It is to be particularly pointed out that, though crankshaft modelling by means of finite elements method would no-doubtfully give excellent results, it is of no practical importance for a classification society surveyor, because he/she needs a simple model and a calculation procedure.
关键词：crankshaft; marine Diesel engine; fatigue strength; IACS UR M53
