A basic study on fatigue gauge made of copper electroplating. 1st report. Effects of understress on slip initiation.

Abstract

Fundamental investigations were made as to slip initiation phenomenon in copper electroplating foil under variable amplitude stress which consists of overstress and understress. The applicability of the foil to the fatigue gauge which detects fatigue damage was discussed. It was found that the modified Miner's rule does not hold for the slip initiation under two-level single block loading composed of overstress and understress. The cumulative cycle ratio in this case is dependent on load histories. Namely, fatigue damage of high-low loading is greater than that of low-high loading and that of two-level multiple loading is the greatest. It was also found that fatigue damage under two-level multiple loading increases as the cycle ratio of overstress to understress increases. This indicates that fatigue damage during understress applied after overstress is greater in the early period of the cycles. The deviation from modified Miner's rule, however, can be said to be small.