Fracture mechanics and the nuclear industry
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I.
INTRODUCTION
W I T H the development of nuclear power plants came the concern for safety and reliability of these systems. Safety requirements for nuclear power plants far exceeded those for most other engineering structures; hence, a more exact method for evaluating safety and reliability was needed. Fracture mechanics provided a quantitative engineering tool for making this evaluation, succeeding where other methods might fail, because it deals with defects in structure. Therefore, fracture mechanics was chosen as a tool for analyzing critical structural components in nuclear power plants. Modem fracture mechanics began in 1957, the same year that Shippingport I, the first commercial nuclear plant, started operation near Pittsburgh, PA. With the development of newer and larger power plants came more difficult structural integrity problems, requiring new developments and approaches in the use of fracture mechanics. In response, each new problem was taken as a challenge to be met; as a result, the fracture mechanics methodology grew to meet the demand of the industry. New developments took the technology from the early days of transition testing, through the days of linear elastic fracture mechanics (LEFM) with the K~c and large specimen testing, into elastic-plastic fracture mechanics (EPFM) with small specimen testing, to R curves and ductile instability, again requiring large specimen tests, and finally into the 1980's, which saw a maturing of the technology, giving rise to the writing of test standards and design codes and the continued solving of new problems. Although other industries had an interest and played a role in the development of fracture mechanics, it was very often the nuclear industry which provided the main motivation. Therefore, fracture mechanics and the nuJ.D. LANDES, Professor, is with the Department of Engineering Science and Mechanics, The University of Tennessee, Knoxville, TN 37996-2030. This paper is based on a presentation made in the symposium "Irradiation-Enhanced Materials Science and Engineering" presented as part of the ASM INTERNATIONAL 75th Anniversary celebration at the 1988 World Materials Congress in Chicago, IL, September 25-29, 1988, under the auspices of the Nuclear Materials Committee of TMS-AIME and ASM-MSD. METALLURGICAL TRANSACTIONS A
clear industry not only came to life the same year, but they continued to grow and develop together. This paper provides a historical description of this development. The intent is not to provide a complete account of the development of fracture mechanics for the nuclear industry but, rather, to describe some of the major developments which illustrate the important role played by the nuclear industry in the past several decades of fracture mechanics development. II.
FRACTURE MECHANICS: THE EARLY DAYS
A historical description of fracture mechanics development usually starts with the work of Griffith in 1921.[1] Although his approach, using energy balance, was not the one ultimately chosen for the modem fracture mechanics, it was re
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