A Study on the High Temperature Creep Crack Growth Properties for Steam Turbine Rotor Steel under Static and Cyclic Loading Condition

J. Ocean Eng. Technol. 1991;5(2):67-75.

O Se-Gyu,Jeong Sun-Eok

화력 발전용 고압 로터강의 정하중 및 변동하중하의 고온 크립 균열전파 특성에 관한 연구

오세규,정순억

부산수산대학교 기계공학과,부산수산대학교 기계공학과

Keywords: Creep Crack Growth, Stress Intensity Factor, Net Section Stress, Transition Creep Region, Steady State Creep Region

핵심용어: 크립 균열 성장 속도, 응력확대 계수, 정미 단면 응력, 천이크립영역, 정상 상태 크립영역

Abstract

The crack length measurements by electrical potential(EP) method for 1% Cr-Mo-V and 12%Cr steel of 0.5T-CT specimen were performed at $500^{circ}C, 600^{circ}C 700^{circ}C$, and an applicability of stress intensity factor($K_I$), net section stress($sigma_{net}$), $C^*$-ingegral and $C_t$ parameter was studied to measure creep crack growth rate(da/dt) with side groove and without side groove under static and cyclic loading condition. The experimental result could be summarized as follows: 1) Crack measurement by EP method was available and coincided with the Johnson, s analytical equation. 2) da/dt by $K_I$ and $sigma_{net}$ was not adequate because of the wide scatter band according to load and temperature, but $C^*$-integral, except for transition region, was adequate. 3) $C_t$ parameter showed the best fitted line through total creep region without relating with both temperature and load condition. 4) Under the cyclic loading condition, $C_t$ parameter was proper to extimate da/dt. And it was shown that da/dt for 1% Cr-Mo V steel under the static condition(R=1) was 1.16 times faster than the case under cyclic loading(R=0), and for 12% Cr steel, 1.43 times.