Diffraction of flexural waves at structural joints

Abstract

This paper discusses flexural wave diffraction at structural joints that connect elastic plates. Transmission and reflection of flexural waves at the joints, as well as their conversion into other types of waves including compressional waves in the plates and sound waves in the surrounding fluid, are examined for various forms of attachments. It is shown that transmission of flexural waves across a structural joint is usually insignificant except for frequencies close to and above the plate coincidence frequency. However, it is found that bending motions may be transmitted through a joint into a structure to energize large amplitude vibrations in the internal structure. It is also shown that acoustic radiation from the wave/joint interactions may occur not only because of direct diffraction of flexural waves at the joints, but also as a result of conversion from nonradiating flexural waves to compressional waves. These waves have supersonic phase speed and may become very efficient radiators if coupled to the fluid; it is shown that the energy level involved in these waves may be much higher than that in the acoustic field due to direct diffraction.