THERMAL FATIGUE EVALUATION METHOD

PROBLEM TO BE SOLVED: To provide a thermal fatigue evaluation method capable of estimating accurately in a short time, a temperature change on the inner surface from a measured temperature on the outer surface of a tubular structure. SOLUTION: This method includes: the first process for expressing a change with time of the inner surface temperature and a change with time of the outer surface temperature of a structure in the form of Fourier series expansion so as to satisfy a heat conduction equation, and comparing each Fourier series expansion term of the change with time of the inner surface temperature and the change with time of the outer surface temperature, to thereby determine a coefficient ratio Mjand a phase delay Δθjof each Fourier series expansion term; the second process for measuring the outer surface temperature of the structure by a temperature sensor; and the third process for developing outer surface measured temperature measured in the second process by the Fourier series, multiplying the coefficient of each Fourier series expansion term of the outer surface measured temperature by the coefficient ratio Mjdetermined in the first process, and shifting the phase of each Fourier series expansion term as much as the phase delay Δθjdetermined in the first process, to thereby estimate the change with time of the inner surface temperature of the structure. The thermal fatigue damage degree of the structure is determined based on the change with time of the inner surface temperature estimated in the third process. COPYRIGHT: (C)2011,JPO&INPIT