The development of novel vibration resistant structures through the use of coupled multi-element configurations
Very often structures are designed to perform a primary function and vibration is an unwanted consequence. It is desirable to develop structural configurations that naturally resist vibration while still satisfying their basic function. This paper describes research to develop structural elements that resist wave propagation and vibration by their natural dynamic character, and not through the use of damping. There are a few well-known examples of such structures. A beam or string placed on an elastic foundation that is either continuous or periodic and discrete can exhibit low frequency cut-off or stop-band behavior in certain frequency ranges. However, many important structures are not able to have elastic attachments to ground and still perform their primary function; a helicopter blade is one important example. Also many structures are subject to stringent constraints, such as weight restrictions. The present work shows that many simple structures can be re-envisioned to have multiple interconnected transmission paths. In certain frequency ranges these structures can be tuned to preclude, or at least greatly reduce, wave propagation and vibration. Three methods to achieve this goal are identified, and sample calculations are presented to illustrate robust, wide-band vibration reduction in various frequency ranges. It is also shown that these methods can be used together to further improve performance. The example structures are constrained to have the same static strength as an equivalent traditional structure with only one transmission path. The vibration characteristics of single element beams and novel multi-element beams are compared, and the multi-element configuration exhibits a dramatic reduction in vibration levels.
