A History Of The Astm E-24 Committee & Its Impact On Structural Integrity
By Paul C. Paris
In 1957 George Irwin told his wife Georgia that it was time for him, as his task ahead, to “spread the message of Fracture Mechanics”. Indeed he began an effective effort to do so. He named the approach “Fracture Mechanics” at that time. In 1958 he presented his methods at the Naval Symposium on Structural Mechanics held at Stanford University, and it was well received. His methods were also well received in other Mechanics circles.
In the late 1950s test firings of the Polaris submarine launched missile resulted in 20 failures of the steel engine case out of 40 test firings. This missile was a major planned US deterrent in the “cold war” situation at that time. These failures were traced to flaws in the welds in the assembly of the engine case. As a consequence the Department of Defense asked ASTM to form a Special Committee to attempt to resolve this problem. The Special Committee at that time did not have the designation as the E-24 committee. That came later.
Professor Jack Low of Carnegie-Mellon University was designated as the committee chairman, and the membership included George Irwin of the Naval Research Laboratory, William Brown and John Srawley of NASA Lewis Laboratory, Charles Tiffany who at Boeing developed the proof test logic for space vehicle pressure vessels, and others. They explored flaw detection techniques and reliable inspection facilities to assure safety of these vessels.
Their activities continued over several years to ensure that the techniques developed were the best for the principle problem that they had resolved. Meanwhile, their meetings occurred several times each year for a day, and then subsequently expanded to a
second day wherein the group reviewed research in progress of the Fracture Mechanics field by many other interested persons, who were invited to present their results. I was myself constantly involved in these secondary activities, which in the early 1960s led to formation of a subcommittee of the Special Committee, on sub-critical crack growth due to fatigue and environmental effects. There was also a significant meeting in Cranfield England, which presented our work at Boeing and of others in Europe, which was mainly aimed at airframe safety.
Also in the early 1960s Syracuse University held a conference at the Sagamore conference center in which many of the presentations discussed fracture and fatigue progress using the Fracture Mechanics approach. Professor Volker Weiss organized the meeting with the sponsorship of the army. Further, in 1964 ASTM held a conference on progress in Fracture Mechanics during their annual national meeting in Chicago. William Brown of NASA Lewis Center organized the meeting so as to cover the overall field as developed at that time. The ASTM Special Technical Publication, STP 381, was a book resulting from that conference, released in 1965, which represented the rapid progress in the field at that time. It was the best-selling book of ASTM! We had all worked very hard on technical papers to cover the part of the field we were assigned to discuss.
Meanwhile, on my return to Lehigh University after 3 years in Seattle, Boeing granted me sufficient funds to begin a fracture research group there. Professors George Sih and Fazil Erdogan joined this effort, which rapidly expanded with other grants from the National Science Foundation, NASA Langley Center and the US Office of Naval Research. Many familiar names in the field were graduate students in this group, such as Richard W. Hertzberg, James R. Rice, James Begley, John Landes, Mathew Creager, Robert Bucci etc. and later Hiroshi Tada. In 1966 at an ASTM meeting in Atlantic City I suggested to George Irwin that, if he would lend his name to support it, we would start a National Symposium on Fracture Mechanics at Lehigh University. The Symposium was initiated in June of 1967 and continued at Lehigh in 1968 and 1969. We also started the Journal of Engineering Fracture Mechanics at that time that still continues to be one of the premier journals in the field of Fracture.
Some months after the first Symposium Irwin was retiring from the Naval Research Laboratory and considering a part time position at another university. With the financial assistance of Boeing, within two weeks, we offered to Irwin the full time position of Boeing University Professor at Lehigh. He accepted and added much to the group. Professor Robert Wei also joined the group.
After the 1969 National Symposium we decided to transfer the sponsorship to ASTM as the leading national society in the field, which led to continuation in 1970 with E. T. Wessel of Westinghouse Research Laboratories in the Pittsburg Area. This choice was made by us, since Wessel had developed an outstanding industrial research group under his leadership there. In addition to Begley and Landes his group included William Clark, William Wilson, and a large testing facility (including testing one foot thick samples of nuclear reactor vessel materials). The group also later acquired Ashok Saxena, Garth Clark, Norman Dowling and Hugo Ernst to round out a most outstanding industrial research group. They made significant progress in many areas of Fracture Mechanics research.
Meanwhile in 1965 ASTM suggested that the Special Committee should become an “E” committee and embark on developing standards for fracture testing materials. The group was formed as the E-24 Committee on Fracture to initially develop a standard test
method for “Plane Strain Fracture Toughness” now denoted as . The group then led by Irwin and Srawley and Brown proceeded with careful work meeting with others, including Wessel, myself and about 5+ others on almost a monthly basis to devise a test procedure which would accurately define as a definitive measurement of the beginning of static growth from a preexisting fatigue crack. It took until 1972 to establish this standard. Indeed, this method now commonly known as the ASTM standard E-399, was worked out carefully so as to be applicable to all metal alloys.
At Lehigh University in 1961 we established a graduate Fracture Mechanics course, which was a regular course for graduate students but also became popular for advanced undergraduates, such as James Rice, etc. This was a first full university course following my course at Boeing in 1959-60. Professor George Sih assisted in the teaching at Lehigh, since I was still officially a graduate student at that time. Beginning in 1967, just before the National Symposium started, we also organized a two week course for people from government laboratories and industry to get an initial understanding of the field. In subsequent years these courses continued as summer courses at University of Denver and many national sites, as well as some international ones. After Irwin joined the staff at Lehigh, he joined in the teaching of regular courses in Fracture Mechanics, as well as having earlier taught in the short courses. These courses had a substantial impact on spreading the knowledge of Fracture Mechanics.
Meanwhile, the ASTM E-24 Committee developed several sub-committees, in addition to that on subcritical growth, including an elastic-plastic fracture subcommittee, a general research subcommittee, in addition to the main committee. In the mid-1960s
the ASTM E-9 Fatigue Committee argued that fracture was simply the last cycle in a fatigue test and crack growth under cyclic load, etc. should be part of their jurisdiction. The 2 committees were not joined then, but a few decades later they were merged into the ASTM E-8 Committee on Fatigue and Fracture. Prior to that merger the E-24 Committee developed standards on elastic-plastic fracture toughness, fatigue crack growth and its threshold, etc. These standard development activities continue today to contribute to the field internationally. The original National Symposium on Fracture Mechanics later included Fatigue and Fracture under the E-8 merger and now joins with other international groups to continue to develop the spreading of further research in the field.
Finally, it is relevant to include a major contribution to the Aircraft Industry as a result of the above developments. In December of 1969 an F-111 aircraft of the US Air Force lost a wing as a result of fracture from a pre-existing crack. This led to making use of the above reviewed research progress to fix this problem. The Australian Air Force also had obtained these aircraft and was also concerned. These aircraft were then proof tested with high loads at cold temperatures and released for flight for a period calculated as safe using these Fracture Mechanics methods. The US Air Force and the civilian US Federal Aviation Authority both adopted as a result, these methods, to assure Structural Integrity of all aircraft. The methods were termed “damage tolerance analysis” and are required as a design criterion. This example shows that the work encouraged and done by the ASTM committees has led to significant applications.