Cold Thermal Fatigue of Austenitic Stainless Steel
To investigate the cold thermal-fatigue characteristics of an austenitic stainless steel (SUS304), a thermal-cycling test was conducted between ambient and cryogenic temperatures. Test specimens were tubes through which flowed liquid helium or nitrogen for cooling and nitrogen gas for warming; the specimen ends were under thermal-deformation restraint. The center of the pipe contained a thin, narrow test section, 20 mm long, to concentrate the thermal deformation. Large hysteresis loops were obtained in the test section. After 757 cycles, a fatigue crack propagated through the wall of the test section, and nitrogen gas leaked into the vacuum chamber. Cold thermal cracks were observed at a corner of the specimen test section; striations were observed on the fracture surfaces.
Cold thermal-fatigue life was estimated from strain-controlled fatigue life. Cold thermal fatigue is a significant factor in the design of cryogenic structures that will experience thermal cycles, especially those where a stress concentration exists.
KeywordsFatigue Crack Fatigue Life Test Section Austenitic Stainless Steel Liquid Helium
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