摘要
为了研究桥梁锈蚀高强度钢丝的疲劳性能以及疲劳断裂机理,并为基于断裂力学理论的锈蚀高强度钢丝疲劳寿命评价提供试验依据,以服役10余年的漂浮结构体系的拱桥吊杆退役钢丝及人工加速腐蚀钢丝为试验样本,对这2类钢丝进行了不同应力幅下的疲劳试验;利用扫描电镜分析了锈蚀钢丝的疲劳断口形貌特征以及疲劳断裂失效过程,对比分析了2类锈蚀钢丝疲劳源的蚀坑尺寸;考察了2类锈蚀钢丝初始裂纹应力强度因子及剩余断裂韧性,并与既有的钢丝疲劳阈值和断裂韧性指标进行了比较;采用三参数公式对锈蚀钢丝应力-寿命(S-N)曲线进行了拟合,对比了不同锈蚀程度钢丝S-N曲线的差异;针对锈蚀钢丝高应力幅的疲劳寿命特征,运用线弹性断裂力学方法对其进行了分析。结果表明:随着腐蚀程度的增加,钢丝的疲劳性能下降;表面蚀坑分布较密时,容易诱发多源裂纹并表现出不规则的裂纹扩展规律;萌生主裂纹的蚀坑阈值条件主要由疲劳裂纹扩展阈值ΔK_(th)控制;锈蚀钢丝S-N曲线在低应力范围下出现拐点,符合三参数公式的拟合规律;锈蚀钢丝的裂纹扩展寿命所占比例较大,基于一定初始裂纹尺寸假设得到的疲劳裂纹扩展寿命SN曲线能较好地反映锈蚀钢丝中等寿命区的平均疲劳行为。
In order to explore the fatigue performance and fatigue fracture mechanism of corroded high-tensile steel wires and provide the experimental basis for fatigue life evaluation of corroded wires in view of fracture mechanics theory, two types of corroded wires were investigated through fatigue tests under different stress amplitudes. One type of the steel wire was sampled from the hangers of a floating-system arch bridge which has served for more than 10 years, and the other type was derived from the steel wires with a treatment of artificial accelerate corrosion. Through the observation of scanning electron microscopic, the fracture surface morphology and the fatigue failure process of corroded wires were analyzed and the crack initiation pitting sizes of the two types of corroded wires were comparatively discussed. The initial-crack stress intensity factors and the residual fracture toughness of the two types of corroded wires were analyzed and compared with the existing indexes of the fatigue threshold and the fracture toughness of steel wires. The S-N curves of corroded wires was fitted by the three-parameter formula and S-N curves of different corroded wires were compared as well. Moreover, the linear elastic fracture mechanics approach was employed to analyze the characteristics of the fatigue life under high stress amplitudes. The results show that the fatigue performance of the steel wires declines with the increase of corrosion degree. Multi-source cracks and irregular crack propagation are easily induced when corrosion pits are dense-distributed. The critical condition for a main crack to initiate mainly depends on the fatigue crack propagation threshold △Kth. The inflection point of the S-N curve arises at the low stress range of corroded steel wires, in correspondence with the fitting rules of the three-parameter formula. Owing to a large proportion of fatigue crack propagation life, the fatigue crack propagation life S-N curves of the corroded steel wires can well reflect the average fatigue behavior in medium fatigue life region by assuming a certain initial crack size.
出处
《中国公路学报》
EI
CAS
CSCD
北大核心
2017年第4期79-86,共8页
China Journal of Highway and Transport
基金
国家自然科学基金项目(51378460)
关键词
桥梁工程
高强度钢丝
断裂力学
断口分析
断裂韧性
疲劳寿命
腐蚀
bridge engineering
high-tensile steel wire
fracture mechanics
fracture surface analysis
fracture toughness
fatigue life
corrosion
