The construction of a prototype apparatus for measurement of elastic constants with small specimen

点击翻译按钮获取中文摘要

The elastic constants are fundamental material constants. Measurements of single crystal elastic constants have been usually performed by ultrasonic techniques, which essentially measure the velocity of elastic waves propagating in a material ; the specimen size required is typically about 10mm in length. It is not always easy to obtain single crystal specimens of such a size, in particular of "new materials". The alternative method which allows the use of smaller specimens is the rectangular parallelepiped resonance (RPR) method.In the RPR method, the measurement of the resonance spectrum is relatively easy, but the analysis of the spectrum to derive the elastic constants is laborious. We have developed a systematic and efficient method of analysis of the resonance spectrum valid for cubic symmetry crystals. The new method allows the analysis by a conventional personal computer. We apply the method to determine of the elastic constants of several intermetallic compounds in wide temperature range, from 77K to 1200K.The resonance frequencies in such a wide temperature range are obtained by a newly constructed apparatus. In the conventional method, the analysis of the RPR spectrum is made without any information on the vibrational mode of each resonance peak. To overcome this essential shortcoming, we have attempted to determine the resonance mode of each resonance peak by measurement of the symmetry of the deformation of the specimen. A new apparatus with two transducers to detect the displacements has been constructed, and used successfully to determine the vibrational mode.