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Measuring bulk material nonlinearity using harmonic generation

机译：使用谐波生成测量散装材料非线性

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摘要

The mechanisms by which a travelling wave propagates through a nonlinear medium are of interest due to the large research effort aimed at exploiting its potential in assessing the damage state of structures. Typically measurements are made to track changing signal nonlinearity due to damage on a single specimen geometry. In this special case relative changes in signal nonlinearity are potentially sufficient to indicate damage. A more robust technique would allow the signal nonlinearity to be related back to the strength of the underlying nonlinear mechanism. In the case of measuring harmonic signal generation in a medium exhibiting a bulk material nonlinearity, a nonlinear parameter exists that relates the material nonlinearity to the measured harmonic signal. However, it is based on the assumption that there is no damping and the excitation is continuous. This paper focuses on assessing the effects of damping, excitation type and signal processing window on the harmonic measurement. Using perturbation and multiple scales techniques, a theoretical model of the generation of nonlinearity is derived. A numerical solution is also developed and both approaches show that the nonlinear parameter first increases and then converges with propagation distance due to the presence of damping. This is experimentally verified. The models also capture the effects of excitation type and signal processing window and using them a correction factor is proposed that accounts for all these effects.
机译：行进波传播通过非线性介质的机理受到人们的关注，这是因为大量的研究工作旨在挖掘其在评估结构损伤状态方面的潜力。通常，进行测量以跟踪由于单个样本几何形状的损坏而引起的信号变化非线性。在这种特殊情况下，信号非线性的相对变化可能足以表明损坏。一种更强大的技术将使信号非线性与底层非线性机制的强度有关。在测量具有大体材料非线性的介质中测量谐波信号的情况下，存在将材料非线性与所测量的谐波信号相关联的非线性参数。但是，它基于以下假设：不存在阻尼并且激励是连续的。本文着重评估阻尼，激励类型和信号处理窗口对谐波测量的影响。使用摄动和多尺度技术，推导了非线性产生的理论模型。还开发了数值解，并且两种方法都表明，由于存在阻尼，非线性参数首先增大，然后随着传播距离收敛。这已通过实验验证。这些模型还捕获了激励类型和信号处理窗口的影响，并提出了使用校正因子来考虑所有这些影响的模型。

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  • 来源
    《NDT & E international》 |2012年第2012期|p.46-53|共8页
  • 作者

    Siming Liu; Steven Best; Simon A. Neild; Anthony J. Croxford; Zhenggan Zhou;

  • 作者单位

    School of Mechanical Engineering and Automation, Beihang University, Beijing 100191, China;

    Department of Mechanical Engineering, University of Bristol, Bristol BS8 1TR, UK;

    Department of Mechanical Engineering, University of Bristol, Bristol BS8 1TR, UK;

    Department of Mechanical Engineering, University of Bristol, Bristol BS8 1TR, UK;

    School of Mechanical Engineering and Automation, Beihang University, Beijing 100191, China;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    nonlinear; harmonic generation; bulk nonlinearity; windowing; attenuation;

    机译：非线性谐波产生体非线性窗口衰减;

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