|Budget Amount *help
¥7,400,000 (Direct Cost : ¥7,400,000)
Fiscal Year 1996 : ¥7,400,000 (Direct Cost : ¥7,400,000)
It is one of very important issues in our society to solve problems in the field of NVH,such as the vibration, noise, and harshness of machines, and to create a life space which is comfortable to human beings. The optimum design method of machine structures, however, has not been established to minimize the noise from machines and to inform the operating state of machines with comfortable and rhythmical sound.
In this research, the structure of insect wings has hence been precisely measured and the natural modes of vibration of the wings have been analyzed to investigate the sound radiation mechanism of the wings of crickets who chirp beautifully. And the natural modes of vibration and the correspondent sound radiation have been studied by modifying the thickness of flat plates partially or by engraving some net pattern on the surface of the plates. The following results are obtained.
(1) Precise measurement of cricket wings
Cricket wings, which have large concave and convex patterns, wer
e precisely measured by the method that the wings were molded with plastic material, cut out little by little, and the sections were photographed. As the results, it has been found that the cricket wings have corrugated strutures.
(2) Vibration mode analysis of cricket wings
The FEM models of cricket wings were produced using the measured data obtained in (1) and their vibration modes were analyzed for various boundary conditions on the root and rubbing parts of cricket wings. Several modes, which largely contribute the sound radiation, were hence found, though the natural frequencies of vibration, which coincided with the frequencies of the main components of cricket sound, were not found.
(3) Natural modes of vibration of plates with net patterns
The natural modes of vibration of plates with net patterns including partially engraved patterns were experimentally analyzed. As the result, it was found that the natural frequencies and the natural modes of vibration changed greatly due to net patterns, and a possibility that sound radiation can be minimized by changing net patterns. Less