TY - GEN
T1 - The law of crack growth life under load controlled creep-fatigue conditions for W-added 12% Cr steel
AU - Nagumo, Yoshiko
AU - Toshimitsu Yokobori, A.
AU - Fukuda, Takahiro
AU - Takahashi, Yoshiki
AU - Sugiura, Ryuji
N1 - Publisher Copyright:
Copyright © 2016 by ASME.
PY - 2016
Y1 - 2016
N2 - W-added 12% Cr ferritic heat resistant steel has been used as a steam turbine rotor material. The turbine rotor material is damaged by high temperature creep and fatigue due to starts and stops and changing load of power generation, which results in crack initiation and growth. In the studies done before, the law of crack growth life under creep-fatigue conditions was characterized and clarified that the characteristics of crack growth life of various load frequencies under different temperatures change from fatigue to creep behavior through an inflection region. The law of crack growth life under creep-fatigue interactive conditions has been reported and evaluated by monotonous linear law. On the other hand, it has been indicated that the characteristics of crack growth life under creep-fatigue condition can be represented mathematically by a three dimensional characteristic curved surface based on non-equilibrium science. In this study, crack growth tests using standardized C(T) specimens of W-added 12% Cr ferritic heat resistant steel were conducted under various conditions of stress holding time, applied stress and temperature. To evaluate the effect of cycle dependent and time dependent mechanisms on crack growth life, a method of separate estimation of cycle dependent mechanism from the time dependent mechanism based on the concept of three dimensional characteristic curved surface based on non-equilibrium science were used. As a result, the effect of load frequency on crack growth life was characterized and the predictive law of crack growth life for W-added 12% Cr ferritic heat resistant steel under creep-fatigue interactive conditions based on the concept of Q∗ with the transition function of crack growth life was estimated.
AB - W-added 12% Cr ferritic heat resistant steel has been used as a steam turbine rotor material. The turbine rotor material is damaged by high temperature creep and fatigue due to starts and stops and changing load of power generation, which results in crack initiation and growth. In the studies done before, the law of crack growth life under creep-fatigue conditions was characterized and clarified that the characteristics of crack growth life of various load frequencies under different temperatures change from fatigue to creep behavior through an inflection region. The law of crack growth life under creep-fatigue interactive conditions has been reported and evaluated by monotonous linear law. On the other hand, it has been indicated that the characteristics of crack growth life under creep-fatigue condition can be represented mathematically by a three dimensional characteristic curved surface based on non-equilibrium science. In this study, crack growth tests using standardized C(T) specimens of W-added 12% Cr ferritic heat resistant steel were conducted under various conditions of stress holding time, applied stress and temperature. To evaluate the effect of cycle dependent and time dependent mechanisms on crack growth life, a method of separate estimation of cycle dependent mechanism from the time dependent mechanism based on the concept of three dimensional characteristic curved surface based on non-equilibrium science were used. As a result, the effect of load frequency on crack growth life was characterized and the predictive law of crack growth life for W-added 12% Cr ferritic heat resistant steel under creep-fatigue interactive conditions based on the concept of Q∗ with the transition function of crack growth life was estimated.
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U2 - 10.1115/PVP2016-63484
DO - 10.1115/PVP2016-63484
M3 - Conference contribution
AN - SCOPUS:85006374923
T3 - American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP
BT - Materials and Fabrication
PB - American Society of Mechanical Engineers (ASME)
T2 - ASME 2016 Pressure Vessels and Piping Conference, PVP 2016
Y2 - 17 July 2016 through 21 July 2016
ER -