Fatigue Crack Growth Rate of SUS 316 and Weld Joint with Natural Crack at 7 K
The fatigue crack growth rate of an austenitic stainless steel, SUS 316, used for support structures of the Large Helical Device was investigated in a helium gas environment at 7 K. The fatigue crack was propagated in the rolling direction of the base plate of 75 mm thick. Also, a multi-pass welded joint was prepared by TIG and MAG welding procedures simulating practical joints performed in construction of the Large Helical Device, and the fatigue crack propagation behavior started from a natural crack at a weld root was investigated. The fatigue crack growth rate in the base metal showed almost the same property as that reported before. Nevertheless, the fatigue crack propagated in the weld metal with a slower rate, about one fourth or one fifth of the rate in the base metal. A compressive welding residual stress around the weld root and a roughness-induced crack closure would be considered to reduce the fatigue crack growth rate. The comparison of these data with those of other cryogenic structural materials, Type 316LN, Incoloy 908, CSUS-JN1, was also performed.
KeywordsFatigue Crack Crack Growth Rate Fatigue Crack Growth Fatigue Crack Growth Rate Welding Residual Stress
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- 3.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
- 4.A. Nyilas, J. Zhang, B. Obst, and A. Ulbricht, Fatigue and fatigue crack growth properties of 316LN and Incoloy 908 below 10 K, Adv. Cryo. Eng., 38: 309 (1992).Google Scholar
- 5.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., AC3, ICMC at Portland, USA, July 1997.Google Scholar
- 6.A. Nyilas, B. Obst, J. Zhang, and W.J. Muster, Cryogenic tensile, fracture and fatigue investigations of nitrogen alloyed stainless steels, Proc. of 2nd Int. Conf. on High Nitrogen Steels, Aachen (1990) p. 191.Google Scholar
- 8.A. Nyilas, B. Obst, and H. Nakajima, Tensile properties, fracture, and crack growth of a nitrogen strengthened new stainless steel (Fe-25Cr-15Ni-0.35N) for cryogenic use, Proc. of 3rd Int. Conf. on High Nitrogen Steels, Kiev (1993) p. 339.Google Scholar