[paper] Crankshaft Design and Fatigue Strength for Marine Diesel Engines

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Authors: Nenad VULIĆ, Ante ŠESTAN, Vedrana CVITANIĆ

Title: Verification of Crankshaft Design and Fatigue Strength for in-line and v-type Marine Diesel Engines
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Published in: Strojarstvo (i.e. Mechanical Engineering Journal), Zagreb, Croatia
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Volume (year) Number: 49  (2007) 4
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7 f! z8 O6 l$ T+ A- ~" s8 N5 B, bPages: 317-331 (total 15 pages)
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/ u( L, z/ a$ |4 T* x  R; ZAbstract: Design appro val of marine Diesel engines crankshafts is , in general, based upon the Technical Rules of classification soci eties. These Rules regularly contain provisions of the IACS UR M53 document: Calculation of Crankshafts for Internal Combustion Engines. The acceptance criteria are related to fatigue strength. The main drawback of this document is that an essential part of the procedure is not defined – how to determine kinematic values and which forces shall be taken into account in the simplified single crank reciprocating mechanism model of in-line and V-type engines. Additionally, as the design approval starts from the cylinder pressure vs. crank angle curve submitted by the engine manufacturer, these values can be used for direct evaluation of torsional vibration excitation forces.
This paper aims to fill the above-mentioned gap, presenting the procedure systematised by the authors to evaluate all the kinematic values and forces relevant for crankshaft fatigue strength validation. The basic idea is to start the analysis from the connecting rod, instead of the piston. The trigonometric approximation procedure for cylinder pressures (necessary for V-type engines crankshaft fatigue strength) and for tangential forces (necessary to determine torsional vibration excitation) is also presented. The entire calculation is illustrated on a selected actual engine example.

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