Elastic characterization of wood by Resonant Ultrasound Spectroscopy (RUS): a comprehensive study
Elastic characterization of wood by Resonant Ultrasound Spectroscopy (RUS): a comprehensive study
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DOI：
10.1007/s00226-017-0980-z
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发表时间：
2018-03-01
影响因子：
3.4
通讯作者：
Arnould, O.
中科院分区：
文献类型：
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作者：
Longo, R.;Laux, D.;Arnould, O.
共振超声光谱（RUS）测量方法的主要原理是激发样品并从其自由机械共振频率推导出其弹性常数。本文的目标是提出 RUS 在木材立方体样品中的应用，方法是：(1) 在迭代数值过程中使用自由共振模式的频率和模态形状（或振动模式）来解决识别样品材料的刚度张量分量的逆问题，(2) 找到木材情况下识别过程的极限并优化其鲁棒性，(3) 将其应用于大密度范围的木材样品。使用特定的连续波作为激励信号，以便通过扫描多普勒测振仪测量以更快的方式通过实验确定样品的自由共振频率和模态形状。然后，通过迭代求解反问题来导出刚度张量。事实证明，在逆识别过程中使用模态振型的增益对于木材来说特别必要，特别是对于将每个测量频率与其相应的理论预测频率进行配对，因为粘弹性阻尼会导致共振峰重叠和/或消失。因此，对每个弹性常数对测量的谐振频率进行了灵敏度分析。它表明，在目前的发展状态下，并不是所有的弹性常数都可以被稳健地识别，因此提出了一种改进的识别程序。这种改进的程序已成功应用于密度范围较大的木材样品，包括软木和硬木，特别是非均质木材品种或具有特定解剖特征的木材样品。
The main principle of Resonant Ultrasound Spectroscopy (RUS) measurement method is to excite a sample and to deduce its elastic constants from its free mechanical resonant frequencies. The goal of this paper is to propose an application of RUS in the case of wood cubic samples by: (1) using frequencies and mode shapes (or vibration patterns) of the free resonant modes in an iterative numerical procedure to solve the inverse problem for identifying components of the stiffness tensor of the sample's material, (2) finding the limits and optimizing the robustness of the identification procedure in the case of wood and (3) applying it to a large density range of wood samples. Specific continuous waves have been used as excitation signal in order to experimentally determine the free resonant frequencies and mode shapes of the sample in a faster way by means of Scanning Doppler Vibrometer measurements. Afterward, the stiffness tensor was derived by solving iteratively an inverse problem. The gain of using the mode shapes in the inverse identification procedure is demonstrated to be particularly necessary for wood, especially for pairing each measured frequency with its corresponding theoretically predicted one, as viscoelastic damping causes the resonant peaks to overlap and/or disappear. A sensitivity analysis of each elastic constant on the measured resonant frequencies has thus been performed. It shows that, in its current state of development, not all of the elastic constants can be identified robustly and a modified identification procedure is thus proposed. This modified procedure has been applied successfully to wood samples with a large density range, including softwood and hardwood, and particularly non-homogeneous wood species or with specific anatomical features.