| Stiffened-plate structures are typically light-weighted structures with high strength and good impact resistance, and therefore have been widely applied to cabins of automobiles, high-speed rail, marine and aerospace, etc. However, vibration and sound are easily aroused in these structures, which seriously influence the comfort. To solve the problem, many researchers have been investigating the vibro-acoustic characteristics of the structures and have reached plenty of achievements. However, the existing researches mainly focus on the validity and accuracy of the methods while rarely summarized and compared the influences of the parameters on the vibro-acoustic characteristics of stifFened-plate structures. Besides, for large structures with multi-stiffeners, many methods are computation-intensive and time-consuming.This study focused on the influence of the parameters of stiffeners on the vibration and sound radiation of stiffened-plate structures. In the first part, the study summarized researches on the vibration characteristics of uncoupled beams and plates based on the theory of Euler beams and thin plates and derived the point mobility of a simply supported beam and plate. Then the first part explained radiation modes, radiated sound power and radiation efficiency of uncoupled beams and plates seperately.The second part firstly derived the expression for the vibration of a simply supported stiffened-plate with diverse connection types under a point force excitation based on the sub-structure transfer matrix method and modal superposition. Then, the validity of the theoretical model was proved by comparing with a FE model and effects of variations of beam’s location and size were discussed. Furthermore, a simplified model of the transfer matrix method in structures with multiple stiffeners was provided and its prerequisite and validity were investigated.In the third part, theoretical derivations of radiated sound power and radiation efficiency were presented and the differences in the influences of parameters on vibration and acoustics characteristics were compared. Finally, an experiment of a clamped stiffened plate was applied to compare the semi-analytical results and directly-measured results and to prove the previous theoretical conclusions.Through the theoretical and experimental results, it was found that both the change of ribs’ mass and stiffeners affects the vibration of stiffened-plate while the influence of the latter was more significant. Besides, the change of force position had a great impact on the space-averaged square velocity as the amplitude of vibration falled when the distance between force location and stiffeners decreased. It was also found that errors for the simplification were attenuated as frequency increased. The simplification became credible when spacing of stiffeners was large enough or there was a large dynamic mismatch between the stiffeners and the plate and the effect of the latter was more predominant than the former. The influence of force position varied when it was located on the beam or on the plate. The calculation error of the former case decreased with the increase of dynamic mismatch while that of the latter increased in contrast. It was also concluded that due to the increase of sound radiation efficiency, the radiated sound power of a stiffened plate might increase in some frequency band even when the space-averaged square velocity decreased. Compared with the effects on vibration responses, the effects of variations of stiffeners on the sound radiation power were more subtle. Though most of analysis was based on a simply supported model, the conclusions might be extended to more complicated cases with the validation from the experiments. |
