Study On Structure Dynamic Characteristics And Optimization Design Of A Bulk Carrier

With the social development and the improvement of living level, people putforward higher requirements to the comfort of living area, and usually harmful vibrationoccurred at aft structure and superstructure, so it’s necessary to research the dynamiccharacteristics of ship structure especially the aft structure and superstructure. This papertook a57000t bulk carrier as the research subject, researched the dynamic responsecharacteristics of its aft structure and superstructure and optimized for them. Followingproblems are contained:(1)The whole ship vibration modal analysis.In this paper. We constructed the wholeship1D ship beam FE model,3D FE model, mixed FE model and finished its modalityanalysis, and then compared and analyzed the calculatetion results.(2)The prediction of the vibration response of aft structure.We took the mixed FEmodel as calculation model and calculated the acceleration response of the aft structureand superstructure under the propeller pressure pulse.We applied the propeller excitationforce in three different methods，compared and analyzed the advantages and disadvantages of the three methods.(3)The modal analysis and prediction of the vibration response.This paper calculatedthe modal of superstructure and each deck’s local modal, and calculated the accelerationresponse of the aft structure and superstructure under the propeller pressure pulse.Afterthat we calculated the acceleration response in wider frequence range being aimed at theposition where the acceleration response was bigger than others.(4)The sensitivity analysis of the aft structure and superstructure.Taking thethickness of plates and the size of stiffness as design variables, we finished the mass sensitivity analysis and response sensitivity analysis under the single frequency excitationforce and the multifrequency excitation force.(5)The single objective optimization for the aft structure and superstructure based ondynamic response prediction.Taking the lightest mass as the objective function, theacceleration response satisfying the vibration standard, we optimized the aft structure andsuperstructure.