The Experimental Research Of Shiphull Structure Vibration And Noise Caused By Icebreaking Work For A River Icebreaker

Icebreaker will be effected by icebreaking load in the process of icebreaking in ice area,ice region ship plates structure will vibrated badly when suffer from the icebreaking load,when the energy of vibrated translate to other region of icebreaker,it will also cause the ship structure in that region vibrated,the enlarge of the response for ship structure vibration and cabin noise caused by icebreaking load may interfere with the normal living and working of crew and passenger.Through the methods of full-scale ship test experiment of icebreaking vibration and noise to analyzing the characteristics of ship structure vibration and cabin noise induced by icebreaking will have an important meaning.The main characters and the icebreaking means of the icebreaker which used for this experiment were introduced in chapter one,the properties and use of transducers for vibrated acceleration and noise in this icebreaking experiment were also introduced;the operation condition of icebreaking test experiment based on the parameters of ice condition and icebreaker speed was made on the basis of overall consideration of the main factors which have an important effect on the ship structure vibration response and ice condition of experiment ice region as well as the icebreaking ability of the icebreaker;the lay-out of transducers of vibrated acceleration and microphone as well as sound level meter were made according to the standards about ship structure vibration and cabin noise,based on the ship structure diagram and cabin arrangement diagram.Both the methods of interception and Short Time Fourier Transform were used to transform the time-domain signal of vibration acceleration amplitude to frequency domain signal which can satisfy the accuracy of analysis;the influence of ice condition and icebreaking speed factors for ship structure vibration induced by icebreaking was analyzed;the response of ship structure vibration will increase as the icebreaking speed increase;the response peak value of vibration acceleration amplitude spectrum in the unbroken ice region are much larger than in the broken ice region where the acceleration amplitude spectrum’s response peak are more single;about three typical position of the center position of local plate,the middle position of beam and the cross of longitudinal aggregate and transverse beam in the main deck and bridge deck region in the icebreaker,its vibration acceleration amplitude will gradually decrease.The ship structure vibration induced by icebreaking could be seen as non-steady random vibration under the continue icebreaking load after analyzing the time-domain curve of structure vibration acceleration.The response of ship cabin noise will increase which will have an influence on the comfortability of main cabins during the process of icebreaking;the response peak value and frequency domain distribution of sound pressure frequency spectrum for different types of cabin;the sound radiation from the ship structure vibration caused by icebreaking load is the main reason that lead the cabins like bridge room that is far from the icebreaking load region and have no equipment noise source in it.,and the change of amplitude in its cabin noise spectrum is mainly in the frequency domain less 200Hz;for cabins that located in the scope of icebreaking load and connect with the outside air,the icebreaking load will impact on its bulkhead and the air noise caused by icebreaking directly transmit to the cabin,which lead to its noise sound pressure spectrum in the middle-high frequency range of 500～2000Hz increase remarkably.As the icebreaking speed rise,the response value in the whole spectrum take on the tendency of enlarge,however,the increment in every center frequency of the octave is distinct for different cabin.The icebreaking load amplitude was calculated by simplifying the form of ship shell plate reasonably in the bow icebreaking load region and adopting ice mechanical strength parameter;the fracture length of ice sheet was estimated based on the feature of time-domain curve of structure vibration acceleration,then the cycle of icebreaking load for three experiment icebreaking speed was calculated;the icebreaking dynamic load model suffer in the bow of the icebreaker in unbroken ice region was established according to the modal of ice sheet fracture and the feature of ship structure vibration response induced by icebreaking.