Improved load ratio method for predicting crack length
- Univ. of Maryland, College Park, MD (United States). Inst. for Systems Research
- Federal Highway Administration, McLean, VA (United States). Turner-Fairbank Highway Research Center
- Naval Academy, Annapolis, MD (United States). Mechanical Engineering Dept.
The elastic compliance from unloading/reloading sequences in a load-displacement record estimates well crack length in elastic-plastic fracture toughness tests of compact tension [C(T)] and bending type specimens. The need for partial unloading of the specimen makes it difficult to run the test under static loading and impossible under either dynamic loading or very high temperatures. Furthermore, fracture toughness testing in which crack length is determined from elastic compliance requires high precision testing equipment and highly skilled technicians. As a result, such tests are confined usually to research laboratories and seldom used under production settings. To eliminate these problems, an improved load ratio method of predicting crack length is proposed that utilizes only the recorded load versus load-line displacement curve (or load versus crack-mouth-opening displacement curve) without unloading/reloading sequences. As a result, the instrumentation is much simpler than in the elastic compliance or potential drop methods. If only a monotonic load-displacement record is to be measured the fracture toughness test becomes almost as simple to perform as a tension test. The method described here improves in three ways the ``original load ratio method`` proposed by Hu et al. First, a blunting term is added to the crack length before maximum load. Second, a strain hardening correction is included after maximum load. And, third, the initial crack length and the physical (final) crack length measured at the end of the test serve to anchor the predicted crack lengths, forcing agreement between predicted and measured values. The method predicts crack extension with excellent accuracy in specimens fabricated from A302, A508, and A533B piping and pressure vessel steels, A588 and A572 structural steels, and HY-80 ship steel.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 136484
- Report Number(s):
- CONF-9305422-; ISSN 0066-0558; TRN: IM9552%%26
- Journal Information:
- American Society for Testing and Materials, Special Technical Publication, Journal Issue: 1251; Conference: Special applications and advanced techniques for crack size tetermination symposium, Atlanta, GA (United States), 19 May 1993; Other Information: PBD: Apr 1995
- Country of Publication:
- United States
- Language:
- English
Similar Records
Critical experiments, measurements, and analyses to establish a crack arrest methodology for nuclear pressure vessel steels. Quarterly report, January--March 1977
Unloading-compliance and load-drop analysis of j/sub ic/ test of irradiated 348 stainless steel. Final technical report