Development of a LASER-Based Resonant Ultrasound Spectroscopy and a Framework for Error Propagation in the Estimated Elastic Moduli

Resonant ultrasound spectroscopy (RUS) is a nondestructive evaluation (NDE) method that uses measured resonance frequencies of a solid to estimate its complete set of elastic moduli. One of the advantages of the RUS method is its applicability to small single crystals. The goal of this project is to measure elastic properties of micrometer sized pillars (micro-pillars) of single crystals and to quantify the level of uncertainties in the measurement. To achieve this goal of resonance frequencies measurements for a micrometer sized specimen, a non-contact detecting technique was needed. A new LASER-based non-contact detecting technique was developed and demonstrated using millimeter sized samples. The measured resonances and the estimated elastic moduli obtained with the LASER-based system are comparable to the results obtained in the traditional contact RUS measurements. In order to determine the level of uncertainties in the estimated elastic moduli using the RUS-based technique, a framework of error propagation for RUS measurement technique was developed and applied to four specimens with different complexities in crystal structures and orientations. The results show that the level of uncertainty increases with increase in material complexities.