Research On Acoustic And Vibration Characteristics Of Typical Ship Structures Considering Welding Residual Stress

Welding technology has been widely used in ship construction.The heating and cooling during the welding process will cause welding residual stress to the structure,which will affect the mechanical properties of the structure.Scholars at home and abroad have researched on the influence of residual stress on the acoustic and vibration characteristics of structures,but have not directly analyzed the influence of welding process parameters on the acoustic and vibration characteristics of structures.A numerical calculation method for the influence of welding process parameters on the acoustic and vibration characteristics of a structure is proposed by combining the thermo-elasto-plastic finite element method and the sound-structure coupling finite element method.This method can directly analyze the influence of welding process parameters on the structure’s acoustic and vibration characteristics.The research results show that residual stress has an important influence on the acoustic and vibration characteristics of the structure.The research can reduce the cost of forecasting the acoustic and vibration characteristics of the welded structure and improve the prediction accuracy,and provide guidance for the formulation of low-noise welding processes.The main research work of this paper is as follows:(1)Numerical method and experimental verification of acoustic and vibration characteristics of typical ship structures considering welding residual stress.The stress-free flat plate and the welded flat plate were selected as the experimental objects.The model design and experimental measurement were carried out to obtain the residual stress distribution,mode shape and natural frequency of the flat plate.The reliability and validity of the numerical method are verified by comparing the numerical simulation results of residual stress and modal with the experimental measurement results.(2)Numerical simulation study of welding residual stress of typical ship structures.According to the typical stiffened plate structure and annular rib structure of ships,three process parameters of welding power,welding speed and welding sequence are selected,and various welding schemes are designed for simulation study of welding residual stress.The structural stress distribution and amplitude of different welding process parameters are analyzed.The results show that the welding residual stress amplitude is less affected by the welding process parameters,and the distribution range is greatly affected.The tensile and compressive stress at the weld is closely related to the welding process parameters.(3)Research on the acoustic and vibration characteristics of typical structures of ships taking into account the welding residual stress.A finite element model of the acoustic and vibration characteristics of typical structures of ships with different welding process parameters is established.By comparing with the calculation results of the acoustic and vibration of the unstressed structure,the influence of the welding process parameters on the structure’s acoustic and vibration characteristics is discussed.The research obtained the natural frequency of the structure,the response of the acceleration level of the characteristic point,the root mean square level of the vibration velocity of the structure,the sound pressure level of the characteristic point in the underwater area and the overall sound power level of the structure,and analyzed the effects of welding power,welding speed and welding sequence on the vibration and acoustic properties of structure.The results show that the low-order natural frequency of the stiffened plate considering the residual stress decreases,and the acoustic and vibration response spectrum curve moves to the low frequency direction.The ring-rib structure is affected by the residual stress.The natural frequency first decreases and then increases with the increase of the order.The acoustic and vibration response spectrum differ significantly at high frequencies.