Fracture Toughness Evaluation of a Round Bar with a Circumferential Notch at Cryogenic Temperature
To characterize fracture toughness of thin plates or local positions in weld joints, a new fracture toughness test method is proposed. A small round bar with a circumferential notch is tensile-tested, and a load-displacement curve is recorded. J-integral is calculated continuously from a load start point to obtain a blunting line empirically. The critical J is determined at the fracture point on the blunting line. Some specimens show remarkable necking, and others fracture at or near the maximum load. Since necking generates a large plastic flow and cup & cone fracture, a flow diagram to evaluate the critical fracture toughness is assessed by adding some limitations. A comparison of results by this new method with ASTM E813-89 is performed, and both methods reveal nearly equivalent toughness value.
KeywordsFracture Toughness Compact Tension Notch Width ASTM Special Technical Publication Critical Fracture Toughness
Unable to display preview. Download preview PDF.
- 1.ASTM E813–89. Standard test method for Jic, a measure of fracture toughness, Annual book of ASTM standards, American Society for Testing and Materials, Philadelphia (1991).Google Scholar
- 3.A. Nyilas and B. Obst, A new test method for characterizing low temperature structural materials, Adv. Cryo. Eng., 42: 353 (1996).Google Scholar
- 4.T. Ogata, K. Ishikawa, T. Yuri, R.L. Tobler, P.T. Purtscher, R.P. Reed, T. Shoji, K. Nakano, and H. Takahashi, Effects of specimen size, side-grooving, and precracking temperature on J-integral test results for AISI 316LN at 4 K, Adv. Cryo. Eng., 34: 259 (1988).Google Scholar
- 5.J.R. Rice, P.C. Paris, and J.G. Merkle, Some further results of J-integral analysis and estimates, in: “ASTM Special Technical Publications 536,” (1973) p. 231.Google Scholar
- 8.A Nyilas, B. Obst, and D.R. Harries, Mechanical investigations on aged stainless steel and Incoloy 908 materials at 4–7 K, Paper will be presented at Adv. Cryo. Eng. (Materials), AC3, ICMC at Portland, USA, July 1997.Google Scholar
- 9.A. Nishimura, J. Yamamoto, O. Motojima, J.W. Chan, J.W. Morris, Jr., R.L. Tobler, H. Takahashi, and S. Suzuki, Fracture toughness of partially welded joints of SUS316 in high magnetic field at 4 K, Adv. Cryo. Eng., 42: 315 (1996).Google Scholar
- 10.A. Nyilas, B. Obst, and A. Nishimura, Fracture mechanical investigations of on aged and aged structural materials with EDM-notched round bars at 7 K, Paper will be presented at Adv. Cryo. Eng. (Materials), HC3, ICMC at Portland, USA, July 1997.Google Scholar