WAVE PROPAGATION IN RODS, SHELLS, AND ROTATING SHAFTS WITH NON-UNIFORM GEOMETRY
WAVE PROPAGATION IN RODS, SHELLS, AND ROTATING SHAFTS WITH NON-UNIFORM GEOMETRY
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发表时间：
2004-03
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通讯作者：
M. Toso
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作者：
M. Toso
通过数值模型和实验测量研究了波在变厚度杆、壳和旋转轴中的传播。所有的数值模型制定使用传递矩阵的方法，准确地再现了所考虑的结构在每个频率的动态行为和波的传播特性。数值预测表明，指数和线性厚度剖面产生的截止频率，低于该频率波不传播沿着的结构。因此，所考虑的棒和壳能够滤除低频，并且它们表现为高通机械滤波器。所考虑的棒和壳类的过滤能力进行了研究，为不同类型的配置文件。此外，通过使用周期性和功能梯度的方式改变结构的材料性能引入的效果进行了研究。线性剖面的影响实际上是通过确定施加在结构一侧的激励的频率和时间响应来评估的。这些结果进行了比较，通过小波变换（WT），同时在时域和频域可视化的结构振动能量的均匀配置文件。理论和实验结果之间的一致性验证了数值模型，并证明了所提出的设计配置在衰减波的传播，特别是在低频范围内的有效性。本文还研究了锥形和阶梯形旋转轴的滤波特性。它被发现，在一个恒定的速度旋转不会显着修改系统的弯曲波传播特性。此外，兴趣扩展到研究的坎贝尔图的锥形和周期性台阶的轮廓。齿轮箱振动通过旋转轴传播的实验证明，锥形和周期性轮廓可以有效地重新分配能量谱，通过限制传播到特定的频带。当轴设置有主动周期性压电插入件时，这种特性变得更加明显。恒定轴向载荷和反馈控制对轴性能的有效性被确定，并与替代的被动周期性处理进行比较。
The propagation of waves in rods, shells and rotating shafts with variable thickness is studied through numerical models and experimental measurements. All numerical models are formulated using the Transfer Matrix approach, which accurately reproduces the dynamic behavior and wave propagation characteristics of the considered structures at each frequency. The numerical predictions show that exponential and linear thickness profiles generate a cutoff frequency, below which waves do not propagate along the structure. Hence, the considered rods and shells are capable of filtering out low frequency and they behave as high-pass mechanical filters. The filtering capabilities of the considered class of rods and shells are investigated for different types of profiles. Furthermore, the effect introduced by using periodicity and changing the material properties of the structure in a functionally graded manner is investigated. The effect of linear profiles is practically evaluated by determining both the frequency and time response for excitations applied at one side of the structure. These results are compared to uniform profiles through the Wavelet Transform (WT), which visualizes the structure vibrational energy simultaneously in both the time and frequency domain. The agreement between the theoretical and experimental results validates the numerical models and demonstrates the effectiveness of the proposed design configurations in attenuating the propagation of waves especially in the low-frequency range. The filtering characteristics are also investigated for rotating shafts with tapered and stepped geometry. It is found out that rotation at a constant speed does not significantly modify the flexural wave propagation characteristics of the system. Also, the interest is extended to studying the Campbell diagrams of tapered and periodically stepped profiles. Experiments on the propagation of vibration from a gearbox through rotating shafts prove that tapered and periodic profiles can effectively redistribute the energy spectrum by confining the propagation to specific frequency bands. Such characteristics become more evident when the shaft is provided with active periodic piezoelectric inserts. The effectiveness of the constant axial loads and feedback control on the shaft performance is determined and compared to the alternative passive periodic treatments.