Time reversal is used as an energy-focusing technique in nondestructive evaluation applications. Here, it is often of interest to evaluate small samples or samples that do not lend themselves to the bonding of transducers to their surfaces. A reverberant cavity, called a chaotic cavity, attached to the sample of interest provides space for the attachment of transducers as well as an added reverberant environment, which reverberation is critical to the quality of time reversal focusing. The goal of this research is to explore the dependence of the quality of the time reversal focusing on the size and geometric shape of the chaotic cavity used. An optimal chaotic cavity will produce the largest focusing amplitude, best spatial resolution, and linear focusing of the time reversed signal. Ultrasonic elastic-wave experiments are performed on a rectangular, cylindrical, and three-dimensional Sinai billiard prism samples, and experiments are repeated each time these samples are successively cut down to smaller volumes. As the size of the cavity decreases, the peak amplitude may increase or decrease depending on the normalization scheme employed. The higher the degree of ergodicity of the cavity, the higher the amplitude and quality focusing achieved.

中文翻译：

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作为空腔体积和几何形状函数的弹性混沌空腔中的时间反转性能

时间反转在无损评估应用中用作能量聚焦技术。在这里，评估小样本或不适合将换能器粘合到其表面的样本通常很有趣。一个混响腔，称为混沌腔，附着在感兴趣的样本上，为传感器的附着提供空间，以及一个额外的混响环境，这种混响对时间反转聚焦的质量至关重要。本研究的目的是探索时间反转质量对所用混沌腔的大小和几何形状的依赖性。最佳混沌腔将产生最大的聚焦幅度、最佳的空间分辨率和时间反转信号的线性聚焦。对矩形、圆柱形和三维西奈台球棱镜样品进行超声波弹性波实验，每次将这些样品连续切割成更小的体积时，都会重复实验。随着腔体尺寸的减小，峰值幅度可能会增加或减少，具体取决于所采用的归一化方案。腔体的遍历度越高，实现的振幅和聚焦质量就越高。