Resonant Ultrasound Spectroscopy estimates the stiffness coefficients of a material from the free resonant frequencies of a single specimen. It is particularly suitable for complete stiffness characterization of anisotropic materials available only as small samples (typically a few mm), and it does not suffer from some limitations associated to quasi-static mechanical test and ultrasound wave velocity measurements. RUS has been used for decades on geological samples and single crystals, but was until recently not applied to mineralized tissues such as bone. The reason is the significant mechanical damping presents in these materials, which causes the resonant peaks to overlap and prevent a direct measurement of the resonant frequencies. This chapter describes the use of RUS for the elastic characterization of mineralized tissues, cortical bone in particular. All steps are described, from sample preparation and measurement setup to signal processing and data analysis, including the developments and adaptions necessary to overcome the difficulties linked to damping. Viscoelastic characterization, from the width of the resonant peaks, is also presented. Mostly technical aspects are developed in this chapter, while the data obtained from RUS on several collections of mineralized tissues specimens are presented and discussed in Chap. 13.
Keywords: Cortical bone; Damping; Elasticity; Inverse problem; Tensor; Vibration; Viscoelasticity.
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