Vibration And Noise Forecasting Of Underwater Complex Shell By Load Identification

Vibration and noise forecasting of underwater complex shell by load identificationLoad identification is to calculate the structural loading conditions using its structural dynamic characteristics and the vibration response obtained under the loads. Load identification plays an important role in the engineering practice, especially in the case of excitation force which cannot be directly measured. Identifying the load of the underwater complex shell and simulating the actual working acoustic-vibration condition of the underwater complex shell at the product design stage have very important significance. This paper focuses on the issues of load identification and vibration and noise forecasting of underwater complex shell. On the basis of the typical structure's load identification, the acoustic-vibration model of underwater complex shell is built and its radiated noise is predicted.First, this paper identified the load of the undamped continuous beam using numerical simulation, comparing the result of identification with the actual force, it shows high accuracy. The experimental modal analysis of typical structure(cantilever beam, plate) is designed to verify the established finite element models. In the single-point excitation mode, response data is measured and load is identified using the FRFs got from both the simulation and test. It shows the results can be improved by selecting appropriate response data.The effective dynamic model of complex shell is built by combination of the modal testing and finite element modeling. Compared with analysis result, the natural frequency error between the dynamic model and experimental results is 10%.The load of complex shell is identified with the noise and vibration test data. In the end, this paper accomplished the calculation of acoustic-vibration coupled case based on the modal, obtained SPL(the sound pressure level) nephogram of the field points and SPL frequency response curve.