Study on the Vibration and Strength of Long-stroke Diesel Engine Crank Shaftings

A caluclation method, by which suitable estimation of vibration and strength concerning crank shaftings of recent 2-stroke cycle marine diesel engine can be obtained, is desired, because other methods proposed before have difficulties in application for such type engines. Theoretical analysis as well as full scale measurement has been carried out in Research Institute of NK, in result, a new analysis system is brought to completion. The system is composed mainly of free vibration analysis routine, forced vibration analysis routine and crank pin fillet strain calculation routine. Evaluation of crank throw stiffness by FEM calculation, a new determination method of crank exciting force, calculation of crank pin fillet strain with a new concept "response factor" which is determined by FEM zooming calculation, are newly introduced. One can analyze torsional, axial and coupled torsional-axial vibration of shafting system and get pin fillet strain wave form including added component induced by the vibration. Calculation results show good agreement with measured ones.