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Proceedings Paper

High-frequency noncontact ultrasonic analysis of materials: introduction and applications
Author(s): Mahesh C. Bhardwaj; Gary F. Stead
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Paper Abstract

High frequency Non-Contact Ultrasonic (NCU) analysis of materials has been a persistent dream of materials engineers and scientists. However, a natural impediment to NCU is the exorbitant acoustic impedance mismatch between air and the test materials. The magnitude of this obstacle is further exacerbated in the Megahertz frequencies, necessary for high resolution, detectability, and sensitivity. This air- material acoustic impedance barrier has been successfully broken by virtue of our phenomenally high transduction piezoelectric transducers (from 100 kHz to 5 MHz) and equally high sensitivity non-contact analyzer (> 150 dB dynamic range and nano-second time-of-flight accuracy). It is now possible to transmit ultrasound in virtually all materials and all states of matter (with the exception of vacuum) without any contact with them. Unlike the conventional contact ultrasound, with NCU, characterization of materials is easy in the early stages of their formation and processing. This includes powders, green ceramics, consolidated powder metals, composite pre-pregs, and polymerization process. In this paper we provide a systematic introduction to the significant of materials characterization, NCU transducers and an analyzer. Also provided are a number of examples of NCU analysis of a wide range of materials, including their internal and surface characteristics. Materials are characterized for thickness, velocity (density and mechanical properties), microstructure, delaminations, defects, etc.

Paper Details

Date Published: 3 August 2001
PDF: 12 pages
Proc. SPIE 4336, Nondestructive Evaluation of Materials and Composites V, (3 August 2001); doi: 10.1117/12.435556
Show Author Affiliations
Mahesh C. Bhardwaj, SecondWave Systems (United States)
Gary F. Stead, SecondWave Systems (United States)

Published in SPIE Proceedings Vol. 4336:
Nondestructive Evaluation of Materials and Composites V
George Y. Baaklini; Eric S. Boltz; Steven M. Shepard; Peter J. Shull, Editor(s)

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