13th International Conference on Fracture June 16–21, 2013, Beijing, China -6- The creep crack initiation times were estimated by Q* parameter, as show in Fig. 10. In Fig. 10, Q* was found to correlate uniquely creep crack initiation for weldment of P92 steel, including of the data for specimen with the notch located in the fine-grained HAZ. 6. Conclusions By conducting more detailed experiments of creep crack growth using a circular notched round bar specimen with variation of notch location in HAZ, the possible presence of an incubation time of creep crack growth was shown, regardless of variation in notch location. We suggested that in order to predict the fracture life for weldment, it is important to clarify the incubation process in order correctly determine the incubation time of creep crack growth. Additionally, the characteristics of creep crack growth rate and creep crack initiation life were summarized in terms of Q* parameter. References [1] R. Sugiura, A. T. Yokobori, Jr., K. Sato, M. Tabuchi, M. Yatomi, K. Kobayashi and K. Nikbin, Strength, Fracture and Complexity, An Int. J., 6 (2011) 177-189. [2] R. Sugiura, A. T. Yokobori, Jr., K. Suzuki and M. Tabuchi, Eng. Frac. Mech., 77 (2010) 3053-3065. [3] A.Toshimitsu Yokoboti. Jr., Ryuji Sugiura, Masaaki Tabuchi, Masataka Yatomi, Kenichi Kobayashi, Kamran Nikbin, Strength, Fracture and Complexity, An Int J., 7 (2011/2012) 315-320. [4] M. Matsui, M. Tabuchi, T. Watanabe, K. Kubo, J. Kinugawa. Degradation of creep strength in welded joint of 9%Cr steel. ISIJ Int. 2001; 41 Supplement: S126-130. [5] K. Ogawa, A. Iseda, Y. Sawaragi, S. Masumoto, F. Masuyama. Development of high strength 12%Cr steel pipe and tubes for boilers. Sumitomo Metals Japan. 1995;47:39-46. [6] H.H. Johnson, “Calibrating the electric potential method for studying slow crack growth,” Materials Research and Standard, 5 (1965) 442-445. [7] K.H. Schwalbe, and D. Hellman, “Application of the Electrical Potential Method to Crack Length Measurements Using Johnson’s Formula,” J. of Testing and Evaluation, 9, 4 (1980) 218-220. [8] T. Adachi, A.T. Yokobori, Jr., M. Tabuchi, A. Fuji, T. Yokobori and K. Nikbin, “The Proposal of Q* Parameter and Derivation of the Law of Creep Crack Growth Life for a Round Bar Specimen with a Circular Notch for Cr-Mo-V Steel,” Materials at High Temperatures, 21, 2, (2004) 95-100. [9] ASTM E1457-07, 2007, “Standard Test Method for Measurement of Creep Crack Growth Times in Metals”. [10] T. Yokobori, T. Iwadate, S. Konosu, M. Tabuchi, A. Fuji, A.T. Yokobori Jr., Strength of materials and fractology, 129 Committee of JSPS: Sasaki Press Japan, 1999, p.291. [11] J.D. Landes, and J.A. Begley, “A Fracture Mechanics Approach to Creep Crack Growth,” ASTM STP., 590 (1976) 128. [12] K. Ohji, K. Ogura and S. Kubo, Japan Soc. Mech. Engng., 44 (1975) 183. (in Japanese) [13] S. Taira, R. Ohtani, and T. Kitamura, “Application of J-Integral to High-Temperature Crack Propagation”, Trans. ASME J. Engng. Mater. Technol., 101 (1979) 154-167. [14] R. Koterazawa, and T. Mori, “Applicability of Fracture Mechanics Parameters to Crack Propagation Under Creep Condition”, Trans. ASME J. Engng. Mater. Technol., 99, (1977) 298-305. [15] A. Fuji, and M. Kitagawa, “A comparison of creep crack growth behavior in Nickel based superalloy with low alloy steel”, Advances in Fracture and Structural Integrity., Prof. of ICF8, V. V. Panasyuk editor., (1994) 487. [16] B. Dogan, and K.H. Schwalbe, “Creep Crack Growth Behavior of Ti-6242”, ASTM
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