盐雾环境下斜拉索应力腐蚀与腐蚀疲劳试验研究

发布时间：2018-01-13 02:10

本文关键词：盐雾环境下斜拉索应力腐蚀与腐蚀疲劳试验研究　出处：《重庆交通大学》2015年硕士论文　论文类型：学位论文

【摘要】：国内外斜拉桥断索事故以及频繁地换索表明,人类在斜拉桥拉索损伤状态评估和剩余寿命预测领域的研究还很不充分。斜拉桥拉索在服役期间由于腐蚀环境和复杂的应力共同作用会使其使用寿命大大缩短,并且在腐蚀介质与交变应力下引起的腐蚀疲劳极易导致拉索发生无预兆的脆性断裂,从而造成巨大的伤亡事故以及经济损失。如何排除上述的隐患成为当今各国科研人员研究的热点。本文通过室内盐雾加速试验,模拟沿海地区斜拉桥拉索遭受氯离子的腐蚀。通过对热包聚乙烯护套的镀锌钢绞线试样进行不同的腐蚀时间以及不同加载状况,来研究钢绞线的腐蚀失重量、力学性能、断口特征等变化情况,分析其产生的原因。本文还创造性地提出,对聚乙烯护套进行不同形式的破坏,进而分析不同破坏形式对钢绞线腐蚀的影响。通过工业数码显微镜与图像处理软件GSA-Image Analyser对腐蚀后钢绞线进行观察与分析,并测量蚀坑与裂纹尺寸,统计蚀坑密度。最后通过已有的研究,推导应力腐蚀与腐蚀疲劳下裂纹扩展速度的算法,并利用有限元软件ANSYS对不同长度、宽度、深度的裂纹进行模拟分析。本文主要内容如下:①通过试验发现,由于氧化产物的保护作用,试验腐蚀中后期腐蚀速率呈下降趋势,并且与自然环境下的腐蚀速率线性无关。②根据灰度直方图所示,腐蚀时间相同的情况下,腐蚀程度表现为:无应力静态应力交变应力。③受拉性能退化的原因主要归于蚀坑的应力集中效应或截面削弱效应;但是,在腐蚀率相差不大的范围内,蚀坑效应的随机特性导致上述受拉性能的退化程度与腐蚀率没有明显的对应关系。④PE护套点破坏与裂纹破坏会引起钢绞线孔蚀与缝隙腐蚀,且这两种腐蚀在交变应力下腐蚀扩展最为严重。⑤影响钢丝断口形状的因素有两个,宏观上表现为蚀坑的几何特征,微观上表现为珠光体团的排列方式。钢绞线的极限抗拉强度是蚀坑的形态与蚀坑底部珠光体团的位向共同作用下决定的。⑥裂纹的深度是影响钢丝抗拉强度以及屈服强度的主要因素,在相同荷载作用下,深度越深裂尖应力则越大;相反,长度与宽度越大,裂尖应力则越小。
[Abstract]:The cable-stayed bridge is broken cable accident and frequently changing cable shows that humans in the cable-stayed bridge cable damage condition assessment and remaining life prediction research is still not sufficient. Cable stayed bridge during service due to corrosion and the complex stress interaction will make the service life is greatly shortened, and the corrosion fatigue in the corrosive medium and under alternating stress caused by cable can easily lead to brittle fracture without warning, causing huge casualties and economic losses. How to eliminate the risks has become a hot topic in today's research. This paper through indoor salt spray test, corrosion of chloride ions in simulated coastal areas of cable-stayed bridge cable. For different etching time and different loading conditions through the strands of heat pack polyethylene sheath of galvanized steel, corrosion of steel strand of the weight loss, mechanical properties, The changes of fracture characteristics, analysis of its causes. The paper also creatively proposed, different forms of damage to the polyethylene sheath, and analyses the influence of different failure modes on the corrosion of steel strand. Through industrial digital microscope and image processing software GSA-Image Analyser on the corrosion of steel strand were observed and analyzed, and the measurement of corrosion pits and crack size statistics, etch pit density. Finally through the existing research, corrosion and corrosion fatigue crack should be derived under the expansion speed algorithm, and the finite element software ANSYS of different length, width, depth of the crack were simulated and analyzed. The main contents of this paper are as follows: through the experiment, the protective effect of oxidation products. Corrosion tests in the late corrosion rate decreased, and the corrosion rate has nothing to do with the linear natural environment. According to the histogram shown, etching time Under the same conditions, the degree of corrosion performance: stress static stress alternating stress. The tensile performance degradation is mainly attributed to the pit stress concentration effect or weaken the effect of cross section; however, in the range of corrosion rate similar to that of the random characteristics of pit, the effect of the tensile properties the degree of degradation and corrosion rate was not significantly related. The PE sheath damage and crack damage point will cause pitting and crevice corrosion of steel strands, and two kinds of corrosion stress corrosion expansion is most serious in alternating. There are two factors affecting the wire fracture shape, exhibited the geometric characteristic of pits the micro performance of the pearlite arrangement. The ultimate tensile strength of steel strand is the common pit pit at the bottom of the pearlite morphology and orientation under the decision. The crack depth is the influence of tensile strength of steel wire and bend Under the same load, the deeper the deeper the depth of the crack tip stress is, the greater the length and width, the smaller the crack tip stress.

【学位授予单位】：重庆交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U446

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