1967 年 16 巻 163 号 p. 228-233
Investigations were made of the 18-8 and 13Cr steels that had been exposed to the thermal fatigue under conditions of transient temperature gradient as to what was the effect of their holding time on them at maximum temperature and what was their crack-growth behavior in comparison with the results of Coffin's type thermal fatigue.
In the case of Coffin's type the thermal fatigue in which the cross-section of specimen was thermal-cycled uniformly and the thermal strain was restrained by outer supports, it was seen that the compressive stress was introduced in the specimen during the holding process at maximum temperature and the thermal fatigue life was prolonged as the holding time was prolonged by the recovery of strain hardening at elevated temperature.
But in the thermal fatigue under conditions of transient temperature gradient, though it had the same relationship between the plastic strain range and thermal fatigue life as that in the Coffin's type thermal fatigue and in addition the crack-growth ratio reduced with increasing the holding time, the thermal fatigue lives decreased as the holding time at maximum temperature was prolonged. It was likely that the working time of tensile stress on heating surface was prolonged by raising the internal temperature of the specimen during the holding process at maximum temperature.