CAJ | 학술논문

选用40Cr结构钢,分别在空气、水和3.5%NaCl水溶液中进行旋转弯曲疲劳实验,研究环境介质对该结构钢高周和超高周疲劳特性的影响.结果表明,40Cr钢在水环境中的疲劳强度比在空气中明显降低;在3.5%NaCl水溶液环境中的疲劳强度比在水中低.断面观察显示,在水和3.5%NaCl水溶液中,疲劳裂纹多源萌生;在稳态扩展阶段,裂纹沿品界扩展并存在广泛分布的沿晶二次裂纹.
선용40Cr결구강,분별재공기、수화3.5%NaCl수용액중진행선전만곡피로실험,연구배경개질대해결구강고주화초고주피로특성적영향.결과표명,40Cr강재수배경중적피로강도비재공기중명현강저;재3.5%NaCl수용액배경중적피로강도비재수중저.단면관찰현시,재수화3.5%NaCl수용액중,피로렬문다원맹생;재은태확전계단,렬문연품계확전병존재엄범분포적연정이차렬문.
Very-high-cycle fatigue of metallic materials is commonly regarded as fatigue failure occurs at stress levels below couventioual fatigue limit and the relevant fatigue lives are above 10~7 cyc. Rotary bending fatigue tests for a structural steel 40Cr were performed in laboratory air, fresh water and 3.5%NaCl aqueous solution, respectively, to investigate the influence of environmental media on fatigue behaviors of the steel in high cycle and very-high-cycle fatigue regimes. The results show that the fatigue strength of the steel in water is remarkably degraded compared with that in air, and the fatigue strength in 3.5%NaCl solution is even lower than that in water. The fracture surface observa-tions show that for the specimens tested in water and 3.5%NaCl solution, multiple crack originations exist and cracks propagate along grain boundary with widespread secondary cracks in their steady propagation period.