抄録
The correlation between crack propagation behavior and variation of cumulative fatigue damage under the multiple repeated two-step stress loading of 70/30 brass was investigated. The experimental results were compared with those of a medium carbon steel (0.46%C) which were obtained in the previous study.
Relationship between crack length and cycle ratio (Σ(nH/NH)+(nL/NL)) under two-step stress loading for 70/30 brass was similar to that under constant amplitude test of σ=σH, that is, almost independent of various combinations and frequency of the overstress σH and understress σL. The values of cumulative fatigue damage D based on the Modified Miner Rule for 70/30 brass were approximately equal to 1.0 regardless of the combination of σH and σL contrary to the case of 0.46%C steel in which D had the values much smaller than 1.0 for a certain combination of σH and σL. Possible reasons such as the crack initiation behavior from the crack tip and the existence of strain aging in carbon steels for different behaviors between 70/30 brass and a medium carbon steel are suggested.
