No abstract

Complex closed shells divided into separate sections by partitions and decks with various kinds of interior equipment are used in the engineering practice quite frequently. The reduction of vibration and noise for these structures is very important at the stage of designing. The authors have developed an energy approach to an acoustic optimization of complex structures. It is based on a minimization of a total structure oscillation energy spectrum. It was indicated that the total oscillation energy estimates vibration and sound radiation of structures quite fully. As an example, the acoustic optimization of the multi-section cylindrical shell equipped with dynamically loaded interior solid bodies was produced with the help of FEM. The reduction of the total oscillation energy was received by changing of partitions stiffness, sizes of separate sections, and dislocations of interior solid bodies for a wide frequency range. The main rules of complex shell structure acoustic designing were formulated as the result of thorough computation investigations.

At low and middle sound frequencies the physical modelling of vibro-absorbing constructions is interpreted as a reconstruction of a frequency dependence of an imaginary part of a full-scale construction dynamic rigidity which is shifted in frequency according to a scale factor. For the high sound frequency range there is a dimensionless form of a matrix energy equation. It allows the task of physical scale modeling to be formulated as a reconstruction of a vibration energy difference between structure elements excited by an external vibration load and the others its elements as in a full-scale object. The analysis is fulfilled in the specially selected frequency bands when the geometrical similarity between scale and full-scale constructions and a number of demands to their material and the loss factors are observed.