Using structural acoustics methods to study new materials.

Abstract

In structural acoustics it is usually necessary to know the vibration properties of the structure under study, and this requires knowing the elastic constants of the materials involved. A relatively recent and powerful method for measuring elastic constants is resonant ultrasound spectroscopy (RUS). Very new and exotic materials for structures often require RUS; the reason is that new materials, when first fabricated, are often available only in very small samples (a few hundred micrometers) or as thin films on substrates, and RUS is the best method for handling such samples. On some occasions samples are fragile or chemically reactive so that they cannot be polished into the shapes required by conventional RUS. Thus, it has been necessary to develop a RUS analysis for arbitrarily shaped samples. This has been accomplished by borrowing a method from structural acoustics: the finite element method (FEM). The discussion of the application of FEM to RUS for arbitrarily shaped samples will include bridging the gap between theory (involving matrices as boldfaced symbols without indices in textbooks on FEM) and actual lines of computer code. Applications of the RUS method for materials will also be discussed.