对超高强度钢和铝合金的研究表明,在压-压交变载荷下缺口前端能引发疲劳裂纹,其门槛值比拉应力高3—4倍。压应力下缺口裂纹长到一定尺寸(如0.2—0.5mm)后就将停止扩展。如果压应力的最小载荷(绝对值)接近零,则裂纹容易形核(门槛值和拉应力相近),且能扩展较长的距离。
Fatigue-crack initiation and growth was investigated by testing an ultra-high strength steel and Al alloy using a notch specimen under cyclic compressive load. Results showed that the fatigue-crack initiation and growth is started from the notch tip and its threshold value △σ_(th) or △K_(th)(ρ) is about 4 times the magnitude of that under tensile load. The crack growth could propagate at a decreasing rate and stop eventually until such length as 0.2—0.5 mm. The threshold value △K_(th)(ρ) under cyclic compressive load would be identical with that under cyclic tensile load and the fatigue-crack could continue to propagate if the minimum cyclic compressive load is near zero. The dα/dN under compression-zero fatigue, however, is 10 to 100 times smaller than that under tensile fatigue.
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