Location

Seattle, WA

Start Date

1-1-1996 12:00 AM

Description

The modern philosopy of materials reliability hinges upon the ability to detect flaws before they reach a critical size that might lead to the failure of a component before the next inspection opportunity. It is the role of nondestructive evaluation (NDE) to provide this capability. In advanced materials such as Al-SiC composites, however, fatigue failure under high stress is governed by the nucleation and growth of a large number of distributed microcracks 1, often much smaller than the detection threshold of conventional NDE techniques (i.e. 200 03BCm). The “fatal” crack forms through the linking of several microcracks. A given fatal crack can spend as little as 5 percent of the fatigue life as a crack detectable by NDE in these materials since some ductility is often sacrificed to achieve their higher strength (i.e. crack instability occurs for crack sizes much smaller than would be expected in conventional alloys). The difficulties that arise for the NDE of advanced materials are that at one end of the fatigue spectrum the microcracks are too small to detect for most of the component’s life. At the other end of the spectrum, by the time a crack long enough to detect appears, failure is imminent.

Book Title

Review of Progress in Quantitative Nondestructive Evaluation

Volume

15B

Chapter

Chapter 5: Engineered Materials

Section

Composite Defects

Pages

1255-1262

DOI

10.1007/978-1-4613-0383-1_163

Language

en

File Format

application/pdf

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Jan 1st, 12:00 AM

Eddy Current Detection of Fatigue Microcrack Distributions in Al-SiC Composites

Seattle, WA

The modern philosopy of materials reliability hinges upon the ability to detect flaws before they reach a critical size that might lead to the failure of a component before the next inspection opportunity. It is the role of nondestructive evaluation (NDE) to provide this capability. In advanced materials such as Al-SiC composites, however, fatigue failure under high stress is governed by the nucleation and growth of a large number of distributed microcracks 1, often much smaller than the detection threshold of conventional NDE techniques (i.e. 200 03BCm). The “fatal” crack forms through the linking of several microcracks. A given fatal crack can spend as little as 5 percent of the fatigue life as a crack detectable by NDE in these materials since some ductility is often sacrificed to achieve their higher strength (i.e. crack instability occurs for crack sizes much smaller than would be expected in conventional alloys). The difficulties that arise for the NDE of advanced materials are that at one end of the fatigue spectrum the microcracks are too small to detect for most of the component’s life. At the other end of the spectrum, by the time a crack long enough to detect appears, failure is imminent.