应力比对TC4-DT钛合金疲劳裂纹扩展速率的影响
Effects of Stress Ratio on Fatigue Crack Growth Rate of TC4-DT Alloy
许 飞, 周善林, 石科学
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作者单位：西北有色金属研究院, 陕西 西安 710016
中文关键字：应力比； 钛合金； 疲劳裂纹扩展速率； 断口形貌
英文关键字：stress ratio; titanium alloy; fatigue crack growth rate; fracture morphology
中文摘要：对TC4-DT钛合金在不同应力比下的疲劳裂纹扩展行为进行了研究，绘制出疲劳裂纹扩展速率和应力强度因子幅值ΔK 之间的关系曲线，用SEM对断口形貌进行了观测。实验结果表明，随着应力比增加,裂纹扩展速率增加；应力比降低，da / dN曲线向高ΔK 方向移动。预裂区主要是以微区解理断裂机制为主，稳态扩展区主要是以疲劳条带扩展机制为主，同时也存在微区解理断裂机制，快速扩展区的断口形貌呈韧窝型静载断裂特征。
英文摘要：The fatigue crack propagation behavior of TC4-DT alloy under different stress ratios was investigated and the fracture surfaces were observed using SEM. The relationship between the propagation rate da / dN and the amplitude of stress intensity factor (ΔK) was drawn using. The results show that the crack growth rate increases with the increase of stress ratio. The decrease of stress ratio makes da / dN curves move to the higher ΔK range. The near-threshold propagation stage gradually disappears. The cracks in the fore-crack region are mainly in the form of micro-cleavage fracture and spread in the form of strip mechanism in the stable spread region with micro-cleavage fracture. The fracture mophology in the fast spread region is dimple-type dead-load fracture.