PSI - Issue 71

P.K. Sharma et al. / Procedia Structural Integrity 71 (2025) 66–73

73

6. Conclusions Various tests are conducted on smooth and notched specimens to determine the effect of multiaxial stresses on creep deformation behavior of alloy 690 material. Following conclusions can be drawn from the study. ● Minimal primary creep was observed for smooth specimen however; the primary creep displacement is much higher for notched specimen. ● The material stays in secondary regime for most of its creep life for both smooth and notched specimens. ● The average hardening exponent is evaluated to be 3.15 while the average value of activation energy is around 345 kJ/mol-K in temperature zone of 800 °C to 1000 °C. These data can be used for simulating the components deformation under notches, discontinuities etc. ● The rupture data of smooth specimen follows a linear relationship with the applied stress value on log-log scale. This data can be used for determination of the representative stresses in the notched specimen. Using these representative stresses, the notch strengthening or weakening behaviour can be computed. ● Alloy 690 material exhibits notch strengthening due to its high ductility in this temperature interval. ● Value of stress triaxiality at middle section of notch increases from 0.388 at notch radius of 2 mm to 0.89 at notch radius of 0.5 mm. The displacement rates are observed to be lower for high stress triaxiality conditions. References Ando, M, Hirose, Y, Karato, T, Watanabe, S, Inoue, O, Kawasaki, N, Enuma, Y., (2014). Comparison and Assessment of the Creep-Fatigue Evaluation Methods With Notched Specimen Made of Mod.9Cr-1Mo Steel. Journal of Pressure Vessel Technology-Transactions of the ASME 136(4). ASTM Standard E8-22. Standard Test Methods for Tension Testing of Metallic Materials. ASTM Standard E292-24. Standard Test Methods for Conducting Time-for-Rupture Notch Tension Tests of Materials. ASTM Standard E3047 – 16. 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