Effect of Specimen Shape on the Low Cycle Fatigue Life of Reduced Activation Ferritic/Martensitic Steel

Abstract

The effect of specimen shape on the low cycle fatigue life of reduced activationferritic/martensitic steel, F82H IEA-heat, was investigated to develop a reliable smallspecimen test technique (SSTT) for fatigue. The low cycle fatigue test was carried out at room temperature in air at a total strain range of 0.8–3.0%. One round-bar-type and three kinds of hourglass-type miniature fatigue specimens were used. The relationship between total strain range (δεt) and number of cycles to failure (Nf) in one of the hourglasstype specimens, which is the current standard miniature fatigue specimen in Japan, was represented by the Manson-Coffin-type regression formula (δϵt = 376N 0.84 f + 2.16N −0.16 f ). The effect of specimen shape on the lowcycle fatigue life and fracture mode was almost negligible among the four specimen types, and their fatigue lives were almost the same. Similar stress distributions at the minimum cross sections of these specimens were shown above the total strain range of 0.8% by elasto-plastic finite element analysis. Therefore, the almost no effect of the specimen shape on the low cycle fatigue life and fracture mode was considered to be due to the similar stress distributions in all the test conditions in this study.