Experimental Investigation of Stress Concentration and Fatigue Behavior in 9% Ni Steel Welded Joints under Cryogenic Conditions

This experimental study delves into the intricate mechanics of stress concentration and fatigue behavior exhibited by 9% Ni steel welded joints under cryogenic conditions. The study specifically examines butt-welded, fillet longitudinal, and fillet transverse specimens, comparing their fatigue prope...

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Bibliographic Details
Published in:Metals (Basel ) 2024-07, Vol.14 (7), p.741
Main Authors: Lin, Yu-Yao, Han, Sang-Woong, Park, Young-Hwan, Kim, Do Kyun
Format: Article
Language:English
Subjects:
9% Ni steel
Bending stresses
Butt joints
Butt welding
butt-welded specimen
Crack propagation
Cryogenic temperature
Deformation effects
Fillets
Finite element analysis
hot-spot stress
Liquefied natural gas
Metal fatigue
Methods
Nickel
Nickel steels
Residual stress
Strain gauges
Stress concentration
stress concentration factor
Welded joints
Wire
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Summary:This experimental study delves into the intricate mechanics of stress concentration and fatigue behavior exhibited by 9% Ni steel welded joints under cryogenic conditions. The study specifically examines butt-welded, fillet longitudinal, and fillet transverse specimens, comparing their fatigue properties under room and cryogenic temperatures. Notably, determining hot-spot stress presents a challenge, as it cannot be directly obtained through traditional means. To overcome this limitation, a method for predicting hot-spot stress is introduced, which considers the effects of misalignments and weld bead characteristics. The study also highlights the impact of grip-clamping-induced specimen deformation and the reduced middle section on stress concentration resulting from misalignments. Furthermore, it proposes separate consideration of the effects of the weld bead on the axial nominal stress and on the bending stress of the specimen. The accuracy of strain gauge measurements in cryogenic environments is addressed by suggesting a method to correct the output of 2-wire strain gauges using a fixed ratio derived from 2-wire and 3-wire strain gauges. By comparing predicted hot-spot stress with actual measurements, the study validates the reliability of the proposed predictive method. These findings contribute to a deeper understanding of the behavior of 9% Ni steel welded joints under cryogenic conditions and provide valuable insights for design and engineering in similar applications.
ISSN:2075-4701
2075-4701
DOI:10.3390/met14070741