Session: ASME Undergraduate Student Design Expo

Paper Number: 172995

Resonant Ultrasound Spectroscopy (Rus) for Determining Elastic Moduli of Soft Materials. 

The elastic moduli of a material gives important information needed for numerous important engineering and scientific applications. Simple techniques for finding them can greatly aid in developing designs by understanding material properties. Based on the classical RUS design [1] we have built an inexpensive but functional instrument for exploring materials elasticity with professional quality. An important advantage of this non-destructive technique is that it allows to quickly obtain the full set of elements of the whole elastic stiffness tensor. In our design the sample is balancing, being nearly freely suspended between two piezoelectric transducers. One transducer serves for excitation of the ultrasound signal; the other one is for receiving of it. The excitation is driven by the internal signal generator of a Stanford Research Systems (SR865A-DSP) lock-in amplifier and voltmeter. Having passed through the sample, the ultrasound wave is received by the other transducer and cleaned up with the lock-in circuitry of the same device. If the frequency of the excitation signal is far away from the internal resonances of the sample, the output signal is nearly zero. However, whenever the excitation occurs at a frequency that matches one of the resonances of the sample, the output signal increases dramatically. The lock-in amplifier is controlled by computer via the standard GPIB interface. A specially written Python code allows us to sweep the excitation frequency with as small increment as needed, and to record a spectrum of resonances of the sample. Data, along with related setup programs and files, are stored on a GitHub repository. Knowing the shape of the sample and its lattice structure, the set of the resonant frequencies allows us to compute the full set of elastic constants for the investigated material. Depending on the choice of piezoelectric transducers, the instrument allows for exploring resonances in the range from few Hertz to several Megahertz, therefore allows to characterize broad range of materials, from very soft to the hard ones. We tested our instrument with transducers made by cutting into ~ 5 x 5 mm2 pieces the commercial lead zirconate titanate 1.7 MHz transducers manufactured by PUI Audio, which we purchased from Mouser Electronics. With these transducers we successfully recorded the resonance spectra of rectangular ferroelectric KTa0.6Nb0.4O3 crystal, and metallic aluminum, iron, and magnesium samples. This data allowed us to elucidate the elastic moduli of these materials, thus confirming the good performance of our setup. An important benefit of our design is that it is relatively simple and modular, which can be adopted for undergraduate education. 

[1] A. Migliori, J. Sarrao, “Resonant Ultrasound Spectroscopy”, 202 p., Wiley-VCH, 1997

This work was partially supported by NSF CMMI # 2337506

Presenting Author: William Adams Gordon College

Presenting Author Biography: Will Adams is an undergraduate researcher at Gordon College, majoring in physics. He works under Dr. Oleksiy Svitelskiy in the Department of Health and Sciences, where his research focuses on material characterization and instrumentation design. His current project involves building and testing a resonant ultrasound spectroscopy system to measure the elastic properties of solids. He is passionate about experimental physics with applications in engineering and plans to pursue graduate studies in the field.

Authors:

William Adams Gordon College
Oleksiy Svitelskiy Gordon College