2018 年 84 巻 863 号 p. 18-00151
In this study, the applicability of cumulative damage law for carbon steel, STS410, was investigated. In addition, prediction method of low cycle fatigue life based on small crack growth was researched. First, low cycle fatigue tests under two step variable loading condition were performed for STS410. Variation of cumulative damage UF at failure fell within general variation range, 0.7 to 1.4. The relationship between crack length and UF was corresponded under different conditions. Crack distribution was also corresponded under different strain range conditions. Therefore, cumulative damage law is available to evaluate the fatigue life of STS410. Next, crack initiation, growth and coalescence behavior of STS410 were modeled, and Monte Carlo simulation was carried out. Fatigue life and crack growth of simulation under strain range constant condition were similar to those of experimental results. In the case of two step loading simulation, simulation results show that UF at failure fell within variation range of strain range constant simulation. These results corresponded to experimental results. Crack length and distribution of simulation also corresponded to those of experiment. Therefore, good agreement can be seen in experiment and simulation, so low cycle fatigue lives of strain range constant and variable loading condition are able to be predicted using present model.