PSI - Issue 68

Takanori Ito et al. / Procedia Structural Integrity 68 (2025) 420–424 Takanori Ito et al. / Structural Integrity Procedia 00 (2025) 000–000

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of cycles to failure in the fatigue test under stress ratio R=0. This revealed that the fatigue characteristics of the welded joints were improved using the developed steel. This result indicates that the fatigue strength of the welded joints of developed steels increases where fractures occur in the HAZ. 4. Summary Our results are summarized as follows. 1. The fatigue strength of the developed steel in the HAZ was found to be superior to that of conventional steel, as demonstrated by fatigue tests using simulated HAZ specimens. 2. The improvement in the fatigue properties of the developed steel is suggested to be attributed to solid solution strengthening, rather than differences in hardness or grain size. 3. It was found that the fatigue strength of cruciform fillet weld joints fabricated with developed steels improves when fatigue cracks originate from the HAZ. References Suzuki, H., McEvily, A, J., 1979, Microstructural Effects on fatigue crack growth in a low carbon steel. Metallurgical Transactions A, 10A, 475. Wasynczuk, J, A., Ritchie, R, O., Thomas, G., 1984, Effects of Microstructure on Fatigue Crack Growth in Duplex Ferrite Martensite Steels, Materials Science and Engineering, 62, 79. Mutoh, Y., Korda, A, A., Miyashita, Y., Sadasue, T., 2007, Stress shielding and fatigue crack growth resistance in ferritic-pearlitic steel, Materials Science and Engineering A, 468-470, 114. Ito, T., Sandaiji, Y., Takashima, Y., Tonan, T., Matsushita, M., Kinefuchi, M., 2023, Improvement of fatigue crack initiation properties using solid solution strengthening, Proceedings in JSME Materials and Processing Conference (in Japanese).