The Study Of The Effect Of Hull Deformation On Ship Propulsion Shafting’s Natural Frequency And Vibration Response

Nowadays,when analyzing and calculating ship propulsion shafting’s naturalfrequency and vibration response, ship hull is generally regarded as a rigid body, thatis to say, applying full constraint to the shafting bearing’s end near to the ship hull.However, although the ship hull has a certain degree of rigidity, hull deformationwould occur definitely during the ship’s actual operation owing to the internal cargoand external wave load,etc. With the wide use of high tensile steel in shipbuildingindustry, ship hull’s rigidity decreases gradually and this phenomenon makes thedifference between ship hull’s rigidity and that of propulsion shafting become moreand more small.At the same time, it also results in the large difference between theactual result and that calculated by traditional method without the consideration of theinfluence of hull deformation on shafting’s natural frequency and vibration response.Therefore, with the more strict requirement about the accuracy of calculating resultand the relative decrease of ship hull’s rigidity, when dealing with the problem aboutshafting’s natural frequency and vibration response, the effect of hull deformationmust be taken in account.In order to obtain the results of ship propulsion shafing’s natural frequency andvibration response when considering the effect of hull deformation and not, aftertaking an8530TEU container ship as the objective and building the hullbottom-propulsion shafting integrated model, this paper then calculates their results intwo above situations respectively by the finite element method. Moreover, for thepurpose of indicating the necessity of considering the hull deformation when slovingthis problem, this paper compares and analyzes the difference between the above tworesults calculated.This paper’s main research contents are as following:(1) Builting up the research objective’s global ship structure model by the finiteelement software ANSYS and analyzing various wave loads under different workingconditions. Then, applying the above wave loads on the global ship structure modelby APDL language and calculating the deformation values at the points where theshafing bearings meet the ship hull. (2) Introducing the classification, harms and corresponding precautions orimprovements about shafting vabration, in addition, and some calculating models andmethods of different types of vibration’s natural frequency and vibration response.(3)Calculating the propeller’s bearing force when it is at78rpm and its advancecoefficient is0.4.(4)Calculating the shafting’s natural frequencies by the hull bottom-propulsionshafting integrated model with and without the consideration of the effect of hulldeformation, and then calculating the vibration response values at the node where theshafting contacts the propeller under the above two situations when taking thecalculated propeller bearing force as the excitation force acting on the hullbottom-propulsion shafting integrated model.(5)Analyzing the effecting principles of the hull deformation on shafting’snatural frequency and vibration response respectively according to the calculatedresults under the two situations.