Non-contact Characterisation of Miniature Piezocrystal Samples
Abstract
Final translation of new piezocrystal materials from the laboratory into Naval SONAR transducersrequires detailed transducer design based on accurately measured material properties.Furthermore, the materials will be subject to high compressive pressure loading in many transducerconfigurations and will generate excess heat under high drive, causing elevated temperatures.Virtual prototyping is now able to take such issues into account but only if the requisite materialproperty matrices are available.The application of elevated temperature and pressure whilst measuring full piezoelastoelectricmatrices is difficult and the literature in this area is very limited. One step towards this is to reducethe constraints placed on the materials by the characterization process. Additionally, the bestestablished process requires multiple samples to be produced, including difficult geometries.Therefore, another step is to reduce the number of samples required for characterization, ideally toone. Finally, larger samples require additional material to be obtained and this can be difficult if onlysmall crystal boules are grown, or small quantities of materials are produced with new compositionsor process. Hence, a final step is to allow characterization of miniature samples, e.g. reducing atypical dimension from 10 mm to 1 mm.This project focuses on these challenges, specifically through the use of laser-generated ultrasound.Already, resonant ultrasound spectroscopy has been demonstrated to be of value in materialcharacterization but it brings difficult measurement processes, constraints on access to the materialsamples during characterization, and the need for complex optimisation to derive the properties.What is now proposed is to use all-optical methods for both excitation of acoustic modes for RUSand read-out of these modes for extraction of material properties. All-optical excitation and readoutmethods also carry the possibility to reduce the sample size since no physical contact is needed,hence reducing the constraints on material mounting and handling.The work will involve the configuration of an appropriate all-optical measurement system, based ona high power Nd:YAG laser operating at 1030 nm, paired with a standard single-axis laser Dopplervibrometer (LDV). In such a system, the sample can be enclosed in an oven with appropriate opticalaccess or can be self-driven for temperature elevation, though the former is preferable for materialcharacterisation. It can also have pressure applied, including via acoustic isolation components.Paralleling the dual temperature elevation mechanisms, pressure can be applied hydrostatically oruniaxially. As the program is exploratory, other instrumentation may be included, such as anadditional single-axis LDV, a 3D scanning LDV, and a low vibration, optically accessible closed-cyclecryostat.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 31, 2020
- Source ID
- N629092012066
Entities
People
- Sandy Cochran
Organizations
- Office of Naval Research
- United States Navy
- University of Glasgow