7:3黄銅の2段繰り返し実験におけるき裂伝ぱ挙動と累積疲労損傷値の変動

概要

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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(n_H/N_H)+(n_L/N_L)) under two-step stress loading for 70/30 brass was similar to that under constant amplitude test of σ=σ_H, that is, aimost independent of carious combinations and frequency of the overstress σ_H and σ_L. 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 σ_H and σ_L 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 σ_H and σ_L. 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.
1992-01-15