Some factors influencing the life of Marine crankshafts 1

The author outlines the principal causes of reduced life in marine oil engine crankshafts and cites typical illustrative examples from service. Reported defects for the various types of crankshaft construction, taken over a ten-year period from January, 1953, are classified and certain conclusions drawn as to relative reliability. Some metallurgical factors are discussed and their influence illustrated

Computer methods are used for evaluating crankshaft torque variations at any section along the shaft from gas pressure diagrams, including the effect of added torsional vibration stresses. A programme is applied to a large modern six-throw two-stroke cycle crankshaft of Rule size with a view to assessing the factors of safety against fatigue failure wider combined bending and twisting with and without torsional vibration, taking into account stress concentration and notch sensitivity, together with an estimate of the effects of misalignment and axial vibration.