Analysis Of Mid-and High-frequency Sound Transmission Of Beam-stiffened Plates

Rib-stiffened plate structures and the sophisticated structures consisted of them have a wide range of applications in the field of mechanical engineering. Rib-stiffened plate structures are widely used as shell structures in automobiles, ships, high-speed trains, air crafts and also all kinds of interior building structures. The vibration and acoustic response of rib-stiffened plate structures has a vital influence for the overall vibration and sound quality of products. It is not only related to the national security, but also infects our daily life. Therefore, scholars of academic circle have been paying great attention to this hot research subject. It is extremely important to make a deep study of this topic in theory, simulation and experiment, and to get a theoretical and technical support of the structures’ material selection and design under different backgrounds of application.Many scholars, domestic and overseas, have been researching on the vibro-acoustic characteristic of both plates and rib-stiffened plate structures, and get a lot of significant achievements. Lots of these achievements have been applied in practice successfully. However, there is not a set of systematic approach to be regarded as the standard modeling guidance to get an accurate calculation of the vibro-acoustic characteristics for stiffened plates, for rib-stiffened plate structures have a complex coupled mode of combining local deformation of short wave and whole deformation of long wave in middle and high frequency. The purpose of this paper is analyzing the modeling of rib-stiffened plate structures in middle and high frequency experimentally and numerically from simple beam-plate structures, combining the common complex structures in practical engineering. The results is especially useful for using the most advanced acoustic analysis software VA One international-to modeling and calculating sound transmission loss.This paper is funded by the National Natural Science Foundation of China (Contract No.51175300):"Dynamic analysis of large complex built-up structures with parameter uncertainties", and the Natural Science Foundation of Shandong Province of China (Contract No. ZR2011EEM009):"Near-high-frequency vibro-acoustic analysis of typical engineering rib-stiffened plates".The main contents and conclusions of the paper are as follows:(1) Vibration analysis. First, starting from the simple beams and plate, analyze their vibration characteristics in middle and high frequency, and then design a structure which contains typical mid-frequency behaviors, finally, determine the vibration frequencies to get a proper method to analyze through the calculation of mode count of combination structure.(2) According to the classification principles of frequency domain above, get an acoustic analyze to the chosen rib-stiffened plate structures in middle and high frequency. First, establish an acoustic analyzing model of the plate in both SEA method and Hybrid method, to get the sound transmission loss. Compare the simulation results to the test results, to prove the validity of the SEA and Hybrid modeling method and the reliability of calculation results of transmission loss.(3) Based on the vibro-acoustic analysis of simple beam-plate structures above, choose complex rib-stiffened plate structures in practice engineering to do the research work. Take the corrugated plate and the driver room for subject, calculating the sound transmission loss of the corrugated plate and the sound pressure level of the driver room under different excitations. Do the acoustic modeling and analyze the sound insulation to the complex rib-stiffened plate structures, and make a related experiment verification.(4) Researches show that:FEA method is mainly suitable for low frequency, deterministic structures. SEA method is mainly suitable for high frequency, uncertain systems. Hybrid method is mainly used in mid-frequency, where there are both deterministic structures and non-deterministic structures in the system at the same time. However, the structure needs to meet a series of certain assumptions, for a correct application of Hybrid method and SEA method, the rationality of modeling depends on the way for the division of each subsystem in the composite structure to a large extent at the same time. Compare the experimental results and simulated ones, we can learn that:the Hybrid method can reflect the actual structures’ sound insulation properties better compared to the SEA method in low frequencies, for the consideration of the influence of boundary conditions in Hybrid calculation model. They can both reflect the general trend of the real structures’ insulation properties result curve in high frequencies. For typical mid-frequency structures, the result curve of Hybrid method can reflect the real insulation properties better. However, for a system that the FE subsystems and the SEA subsystems have a similar mode count, the Hybrid method having a result curve almost the same as the SEA method, and its time-consuming is far greater than the latter.