Raising natural frequencies of a structure via surface-grooving technique

Abstract

Structural dynamics modification (SDM) is a very effective technique to improve a structure's dynamic characteristics by adding or removing auxiliary structures, changing material properties and shape of structure. Among the SDM techniques, changing or modifying structure shape to raise its natural frequencies has been mostly relied on engineer's experience and time-consuming trial-and-error process. To develop a systematic method to modify structure shape, surface-grooving technique is studied. In this work, the shape of base structure is modified to improve its dynamic characteristics such as natural frequencies via surface-grooving technique. Grooving shape is formed by merging the neighboring small embossed elements after analyzing frequency increment sensitivities of all the surrounding embossed elements. All this process is targeted to pack in a software to get an optimum grooving shape automatically. In this package, the initial grooving position starts from the element having the highest modal strain energy then it expands into neighboring elements. The range of grooving area for checking its frequency sensitivities is restricted only to their surrounding elements to reduce its computation effort. The developed algorithm was tested with an L-shaped plate and hard disk drive (HDD) cover to raise its natural frequency by giving some groove on its surface. Also, the grooved HDD cover design was manufactured using rapid prototyping and tested to prove the effectiveness of the surface grooving as a SDM tool.