Functional Morphology and Biomechanics, Institute of Zoology, Kiel University, Kiel, Germany.
School of Engineering, London South Bank University, London, England.
Naturwissenschaften. 2021 Dec 3;109(1):1. doi: 10.1007/s00114-021-01773-7.
The avian feather combines mechanical properties of robustness and flexibility while maintaining a low weight. Under periodic and random dynamic loading, the feathers sustain bending forces and vibrations during flight. Excessive vibrations can increase noise, energy consumption, and negatively impact flight stability. However, damping can alter the system response, and result in increased stability and reduced noise. Although the structure of feathers has already been studied, little is known about their damping properties. In particular, the link between the structure of shafts and their damping is unknown. This study aims at understanding the structure-damping relationship of the shafts. For this purpose, laser Doppler vibrometry (LDV) was used to measure the damping properties of the feather shaft in three segments selected from the base, middle, and tip. A combination of scanning electron microscopy (SEM) and micro-computed tomography (µCT) was used to investigate the gradient microstructure of the shaft. The results showed the presence of two fundamental vibration modes, when mechanically excited in the horizontal and vertical directions. It was also found that the base and middle parts of the shaft have higher damping ratios than the tip, which could be attributed to their larger foam cells, higher foam/cortex ratio, and higher percentage of foam. This study provides the first indication of graded damping properties in feathers.
鸟类的羽毛兼具坚固和灵活的机械性能，同时保持重量轻。在周期性和随机动态负载下，羽毛在飞行过程中承受弯曲力和振动。过度的振动会增加噪音、能量消耗，并对飞行稳定性产生负面影响。然而，阻尼会改变系统的响应，从而提高稳定性并降低噪音。尽管羽毛的结构已经得到了研究，但它们的阻尼特性知之甚少。特别是轴的结构与其阻尼之间的联系尚不清楚。本研究旨在了解轴的结构-阻尼关系。为此，使用激光多普勒测振仪（LDV）测量了从基部、中部和尖端选择的三个区段中的羽毛轴的阻尼特性。扫描电子显微镜（SEM）和微计算机断层扫描（µCT）的组合用于研究轴的梯度微观结构。结果表明，当在水平和垂直方向上机械激励时，存在两种基本振动模式。还发现轴的基部和中部的阻尼比大于尖端，这可能归因于其较大的泡沫细胞、较高的泡沫/皮质比以及较高的泡沫百分比。本研究首次表明羽毛具有分级阻尼特性。
