Material Research Centre, Department of Mechanical Engineering, University of Bath, Bath, BA2 7AY, United Kingdom.
J Acoust Soc Am. 2012 Jun;131(6):4316-23. doi: 10.1121/1.4707522.
This paper presents a nonlinear imaging method for the detection of the nonlinear signature due to impact damage in complex anisotropic solids with diffuse field conditions. The proposed technique, based on a combination of an inverse filtering approach with phase symmetry analysis and frequency modulated excitation signals, is applied to a number of waveforms containing the nonlinear impulse responses of the medium. Phase symmetry analysis was used to characterize the third order nonlinearity of the structure by exploiting its invariant properties with the phase angle of the input waveforms. Then, a "virtual" reciprocal time reversal imaging process, using only one broadcasting transducer and one receiving transducer, was used to insonify the defect taking advantage of multiple linear scattering as mode conversion and boundary reflections. The robustness of this technique was experimentally demonstrated on a damaged sandwich panel, and the nonlinear source, induced by low-velocity impact loading, was retrieved with a high level of accuracy. Its minimal processing requirements make this method a valid alternative to the traditional nonlinear elastic wave spectroscopy techniques for materials showing either classical or non-classical nonlinear behavior.
本文提出了一种用于检测具有漫射场条件的复杂各向异性固体中冲击损伤引起的非线性特征的非线性成像方法。所提出的技术基于反滤波方法与相位对称分析和调频激励信号的组合，应用于包含介质非线性脉冲响应的许多波形中。相位对称分析用于通过利用输入波形的相位角的不变特性来表征结构的三阶非线性。然后，使用仅一个广播换能器和一个接收换能器的“虚拟”互易时间反转成像过程，利用多线性散射作为模式转换和边界反射来激励缺陷。该技术在受损夹层板上进行了实验验证，并以高精度恢复了由低速冲击载荷引起的非线性源。其最小的处理要求使得该方法成为传统非线性弹性波光谱技术的有效替代方法，适用于表现出经典或非经典非线性行为的材料。
