疲労に関する研究（第6報）磁歪応用による金属の疲労に関する研究

Abstract

In this report I studied the change of the internal strain along with fatigue for the specimens of carbon steel, (0.4%C) pure iron and nickel by using the same apparatus as in the previous report. The results are briefly summarized as follows: (1) By Inverse-wiedemann Effect, even the small strain can be measured very sensitively and quickly, that is, the existence of the fatigue can easily be detected. (2) If the load is classified into three kinds,-larger, less than the fatigue limit and equal to the fatigue limit-the process in which the value of the induced current changes with the propagation of the fatigue is almost similar in spite of the difference in the specimens. The heavier load is, the larger the fluctuation of the value is and the amplitude gradually reaches a small value if the load approaches the fatigue limit. Under the load less than fatigue limit the fluctuation of the induced current is very sensitively recognized in the early stage of the fatigue but it soon reaches the stationary value. (3) At Exciting current of 10A, the maximum value of the induced current was about 35 μA in carbon steel, 60 μA in pure iron, and almost zero in nickel. But if the exciting current is raised to 25 A, we can recognize the value larger than zero even in nickel. (4) If we measure the residual stress caused on the fatigue by Inverse-Wiedemann Effect, the value becomes about 3.5 kg/mm3 in carbon steel and 0.21 kg/mm2 in nickel. Considering the internal changes of material caused on fatigue very small, it is very interesting that the residual stress is very small in comparison with that of the specimen cut by a lathe, in spite of the fact that my method is different from the ordinary ones. (5) It was recognized that the internal strain would disappear in early stage of the fatigue when the specimen has residual stress. This phenomenon was same as the result published in my fifth report. (6) Each fatigue limit of carbon steel (0.4%C), pure iron and nickel was 17.2 kg/mm2, 9.2 kg/mm2, and 11.5 kg/mm2, and each proportional limit was also about 18.5 kg/mm2 in cardon steel and 8.5 kg/mm2 in pure iron.