Psychological Sciences, The University of Melbourne, Melbourne, Victoria 3010, Australia.
J Acoust Soc Am. 2012 Jan;131(1):926-34. doi: 10.1121/1.3651255.
Prestresses are purposefully added to an object to improve its performance, such as tuning a guitar string by adding tension. This paper reports how the normal modes of a sheet metal component can be tuned through the prestresses generated by cold-forging small dimples. Finite element analysis showed that the frequencies of specific mode shapes were differentially affected by the location of residual stress fields due to dimple formation in relation to modal stress fields. The frequencies of overtones were most sensitive to the depth of the dimples located near the maxima of modal stresses. Using this approach a series of musical gongs were designed with up to the first five overtones tuned to within 5% of the harmonic series. The balance of harmonic and inharmonic overtones in these gongs that are well resolved by the human cochlea may constitute a set of recognizable musical timbres with sufficient harmonicity to produce an unambiguous pitch for most listeners. Since many other mechanical properties of sheet metal components are affected by residual stresses this manufacturing technique may have broader application in design engineering.
预应力被有意地施加到物体上以提高其性能，例如通过增加张力来调整吉他弦。本文报告了如何通过冷锻制小凹痕产生的预应力来调整金属板部件的固有模态。有限元分析表明，由于凹痕形成引起的残余应力场相对于模态应力场的位置，特定模态形状的频率会有差异。由于位于模态应力最大值附近的凹痕深度不同，泛音的频率对其最为敏感。通过这种方法，设计了一系列的音乐锣，其中前五个泛音的频率被调谐到谐和系列的 5%以内。这些锣中谐波和非谐波泛音的平衡被人类耳蜗很好地分辨出来，可能构成一组可识别的音乐音色，具有足够的谐和性，以便大多数听众能够产生一个明确的音高。由于金属板部件的许多其他机械性能都受到残余应力的影响，因此这种制造技术在设计工程中可能有更广泛的应用。
