We experimentally investigate and characterize high order Lamb wave modes in a dry human skull. Specifically, we show that the diploë supports distinct wave modes in the sub-1.0 MHz frequency regime, and we employ these modes for the estimation of equivalent mechanical properties of cortical and trabecular bones. These modes are efficiently generated in a parietal region by direct contact excitation with a wedge beam transducer, and are recorded via infrared laser vibrometry. Frequency/wavenumber data are estimated using a matrix pencil method applied to wavefield measurements recorded on the outer cortical surface. The semi-analytical finite element model of an equivalent three-layered plate provides the platform for the identification of wave modes based on their through-the-thickness profiles, and supports the estimation of equivalent mechanical properties in conjunction with an optimization algorithm developed for this purpose. The results presented herein illustrate how high order Lamb waves can be used to gain understanding of the wave properties of a human skull and to estimate the orthotropic and equivalent isotropic mechanical properties of cortical and trabecular bones.

我们实验研究和表征人类干颅骨中的高阶Lamb波模式。具体来说，我们证明了该双底波在1.0 MHz以下的频率范围内支持不同的波模，并且我们将这些波模用于估算皮层和小梁骨的等效力学性能。这些模式是通过楔形光束换能器的直接接触激励在顶区有效产生的，并通过红外激光振动法记录。频率/波数数据是使用矩阵铅笔方法估算的，该方法适用于皮质外表面记录的波场测量。等效三层板的半解析有限元模型为基于波厚分布的波模识别提供了平台，并结合为此目的开发的优化算法来支持等效机械性能的估算。本文介绍的结果说明了如何使用高阶Lamb波来了解人类头骨的波特性并估计皮质和小梁骨的正交各向异性和等效各向同性的力学特性。