変動ひずみ条件下におけるタービンロータ材の高温疲労特性とその評価法

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The effect of service loading on the fatigue behavior of steam turbine rotor steel (1Cr-1Mo-1/4V steel) was studied at 550℃. The service loading was simulated by a multiple two-sep straining. Under the programmed fatigue tests the life was reduced remarkably (1/10〜1/100), as compared to the estimated values based on the conventional methods using a linear cumulative law in terms of fatigue and creep damages. This decrease in fatigue life was largely attributed to the accumulation of increased plastic strain range corresponding to the small strain cycles after large strains. For the programmed fatigue test, the fatigue life was estimated under the assumption of linear cumulative fatigue damage law in terms of the measured plastic strain range. The results of this estimation were in agreement with those of the constant strain range test. The plastic strain range which increased after a large strain cycle could be expressed as a relatively simple function of strain conditions. This was indicative of a possible system for monitoring fatigue life of turbine rotors by using the above-mentioned linear cumulative damage law. The fatigue curve could be modified with the data above so as to estimate fatigue life under variable strain for use in designing. It was shown, however, that the curves were affected largely by the number of cycle of small strains (n_2) and tended to increase in life with n_2. The significance of further examinations on the effects of service loading s was indicated.
1985-02-15

変動ひずみ条件下におけるタービンロータ材の高温疲労特性とその評価法

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