Analysis Of Intermediate Stiffeners Effects On Sound Transmission Of Intermediate Stiffened Double Plates

With the rapid development of science and technology, the improvement of people’s living and spiritual standard, It requires not only reduce the time spending in traffic traveling time, but also, it is hoped that they can feel comfortable and cozy in the event of traffic. Thus, the noise control measures of the high-speed rail, aircraft, cars and other high-speed transport have received an increasing attention. Rib-stiffened plate structures are widely used as the floors and the shell structures of the high-speed transport. Under the motivation of the structure acoustic loading, they can not only radiate the noise to the outside, but also can be used to control the transmission of the noise. Therefore, their vibro-acoustics properties can seriously affected the quality of the sound quality of the vehicles, and at the same time, affect the life index of people’s life. As a result, the study of sound and vibration characteristics and sound insulation property of the rib-stiffened plate structures have caused the majority of scholars’ attention. Double rib-stiffened plates are particularly representative of the rib-stiffened plate structures. However, despite of such a fast that the research from scholars at home and abroad has achieved significant progress regarding on double rib-stiffened plates, relatively very few of publications are about the parameter sensitivity study of the stiffeners on the vibro-acoustics of double rib-stiffened plates as a whole. With the above in mind, under the sponsorship of the National Natural Science Foundation of China (NO.51175300) and the Natural Science Foundation of Shandong Province (NO. ZR2011EEM009), the present research is focused on analyzing the sensitivity of the sound and vibration characteristics and the sound insulation of the double rib-stiffened plates about the intermediate stiffener height, spacing, and other parameters.The main contents and conclusions of this paper are as follows:(1) In the aspect of theoretical knowledge, the paper describes the theoretical knowledge about vibro-acoustics characteristics of the plate in detail. First of all, the structural modal characteristics of thin plate structures are verified by comparing the theoretical and numerical results. Then, the theory of the sound insulation characteristic of the plate are introduced, followed by comparisons between the theoretical, experimental, and numerical results of the sound insulation of the plate in terms of sound transmission loss (STL). Finally, the dissertation discusses the sound insulation theory of the double plate structures and that of the double rib-stiffened plate structures.(2) In the aspect of the vibro-acoustics, the paper uses the software VA One to build the model of the double rib-stiffened plate structures, and analyzes the influences of rib-stiffeners on the vibro-acoustics of a double stiffened plate. Finally, the paper discusses the sensitivities of the rib-stiffeners on affecting the vibro-acoustics of a double stiffened plate. It is concluded that increase of space between stiffeners results in decrease in the natural frequency of the double rib-stiffened plates and the frequency of peaks on the sound radiation power curve or vice versa. Besides, the influence of space on the natural frequency becomes more significant when frequency increases. With the height of the rib-stiffeners increasing, the natural frequency of the double stiffened plate increases, the valley of the sound radiation power curve moved to the high frequency. With the frequency increases, the influence of the height on the natural frequency is decreasing.(3) In the aspect of the sound transmission loss, according to the modal number in the third-octave bandwidth, the whole frequency region is divided into the low-middle frequency and the high-frequency. In the low and middle frequency region, the former FE model is validated by the equivalent modeling theory. While at high frequency, the analysis is based on MATLAB programs. Still, space and height of the stiffeners fluctuates and their effects on STL of the structure are discussed. It is found that, similarly, the increase of space results in the decrease in valley frequency of STL curve while the effect of height is exactly the opposite.