2019 年 4 巻 p. 90-95
The influence of load frequency on a cyclic stress measurement method using electrodeposited copper foil is investigated in this study. The copper foil is obtained by electroplating, and the foil is adhered onto the surface of a plate-type specimen made from carbon tool steel. After cyclic loading tests are performed at three different load frequencies, the densities of grown grains occurring in the copper foil are measured using an optical microscope and an image processing software. The experimental results reveal that the strain sensitivity of the grain growth tended to increase slightly with decreasing load frequency. When the difference in the load frequency is about two times, the influence of frequency on the grain growth density is small. On the other hand, when the difference reaches about ten times, a measurement error of about 10% occurs. Therefore, it became clear that it is necessary to consider the influence of load frequency in order to measure stress more accurately. In this study, the conventional calibration equation for stress measurement based on the grain growth density was modified to a new expression that takes into consideration the influence of load frequency.
