Acoustic Microscopy Applied to Ceramic Pressure Vessels and Associated Components

[+] Author and Article Information
Chiaki Miyasaka1

 The Pennsylvania State University at University Park, 212 Earth and Engineering Science Building, University Park, PA 16801

Bernhard R. Tittmann

 The Pennsylvania State University at University Park, 212 Earth and Engineering Science Building, University Park, PA 16801


Presently at the Idaho National Engineering and Environmental Laboratory.

J. Pressure Vessel Technol 127(3), 214-219 (Jan 31, 2005) (6 pages) doi:10.1115/1.1990212 History: Received January 25, 2005; Revised January 31, 2005

Alumina ceramic is being used extensively for external pressure vessels in naval applications. The material is also used in valves and other components, where reliability, immunity from corrosion, and high temperatures are required. This report presents a technique for the nondestructive evaluation of alumina ceramic components. The cracks were produced by CO2 laser radiation. Since there is a need for the detection of very fine cracks, scanning acoustic microscopy was found to be superior to optical methods for imaging surface and subsurface cracks. We address the issue of crack initiation with the use of postirradiation analysis. This article reports our results on the evaluation of the surface and interior cracks with optical, scanning laser, scanning electron, and scanning acoustic microscopy. We present images of surface and subsurface microcracks generated at different power levels of a high power CO2 laser system. The spatial variation of the Rayleigh wave velocity is measured by the V(z) curve technique. These preliminary data suggest that, with some improvement, the V(z) technique may detect residual stress with high spatial resolution.

Copyright © 2005 by American Society of Mechanical Engineers
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Figure 1

Surface roughness measurement for Type I specimen with LSCM

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Figure 2

Schematic diagram of the laser shaping apparatus

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Figure 3

The crater caused by the deformed beam for Type I specimen. The image is formed by the SAM. When visualizing the surface of the specimen, the acoustic lens is focused on the specimen (we denote z=0μm), and when visualizing a subsurface of the specimen, the acoustic lens is mechanically defocused toward the specimen (we denote z=−xμm, where x is the defocused distance). The surface image (Z=0μm) and the interior images (Z=−10μm, and −20μm) are superimposed into one image (3Z mode image) for better understanding.

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Figure 4

Schematic diagram of SAM

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Figure 6

Schematic diagram showing the principle of the V(z) curve

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Figure 7

The V(z) curve for alumina (Type II), wherein the curve was formed with the point focus acoustic lens with frequency at 400MHz, and wherein water at 20°C was used for a coupling medium.

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Figure 8

Measuring points on the surface of the specimen

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Figure 9

Optical image (reflection)

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Figure 10

Optical image (transmission)

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Figure 11

Optical image of alumina plate after laser irradiation: (a) horizontal section, (b) vertical section; bar: 100μm.

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Figure 12

SEM images of alumina plate after laser irradiation

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Figure 13

SAM images, wherein the images were formed with frequency at 400MHz using the point focus acoustic lens. Bar is 400μm.



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