酸雨环境下Q420B钢材腐蚀疲劳裂纹扩展试验与模型研究  

Experimental and model study on corrosion fatigue crack propagation of Q420B steel in acid rain condition

作　　者：杨晓阳 范文亮[1,2] 李正良[1,2] 祖云飞 Yang Xiaoyang;Fan Wenliang;Li Zhengliang;Zu Yunfei(School of Civil Engineering,Chongqing University,Chongqing 400045,China;Key Laboratory of New Technology for Construction of Cities in Mountain Area(Chongqing University),Ministry of Education,Chongqing University,Chongqing 400045,China)

机构地区：[1]重庆大学土木工程学院,重庆400045 [2]重庆大学山地城镇建设与新技术教育部重点实验室,重庆400045

出　　处：《土木工程学报》2023年第2期1-11,共11页China Civil Engineering Journal

基　　金：国家自然科学基金(51678092)。

摘　　要：为研究特高压输电塔所用Q420B结构钢在酸雨环境下的腐蚀疲劳裂纹扩展行为,开展了Q420B的CT试样在人工酸雨喷雾腐蚀环境下的腐蚀疲劳试验。试验采用背面应变法监测裂纹长度,研究喷雾方式、pH值、应力比对裂纹扩展速率的影响。试验现象及断口分析表明,CT试样的断裂类型主要为穿晶疲劳断裂,腐蚀疲劳机制主要为阳极溶解机制。对于各工况,基于Paris模型推导了考虑模型参数随机性及da/dN数据波动性的腐蚀疲劳裂纹扩展速率P-da/dN-ΔK模型。结果表明,腐蚀疲劳裂纹扩展速率的离散性随应力强度因子幅的增大呈先减小后增大的趋势,该现象与Paris模型参数的线性相关性有关;相较于浸泡腐蚀,喷雾腐蚀下的裂纹扩展阶段存在明显的裂纹闭合效应,导致在ΔK较低阶段喷雾工况裂纹扩展速率均低于纯疲劳工况;腐蚀液pH值越低,裂纹扩展速率曲线斜率越大,但其初始速率也越低;应力比方面,增大应力比能明显缓解裂纹闭合效应,且裂纹扩展速率随应力比的升高而升高。To study the corrosion fatigue crack propagation behavior of Q420B steel used in UHV transmission towers in acid rain condition,the corrosion fatigue experiment of CT specimen of Q420B under artificial acid rain spray was conducted.The crack lengths were monitored by backface strain technique.The effects of spray mode,pH value and stress ratio on corrosion fatigue crack growth rate were studied.Experimental phenomenon and fracture analysis show that the fracture type of CT specimens is mainly transgranular,and the corrosion fatigue mechanism is mainly anodic dissolution.Based on the Paris model,a P-da/dN-ΔK model of corrosion fatigue crack growth rate considering the randomness of the model parameters and the volatility of da/dN data is derived.Analysis results disclose that:the discreteness of the corrosion fatigue crack growth rate tends to decrease and then increase with the increase of the stress intensity factor range,which is associated with the linear correlation of the Paris model parameters;compared with immersion corrosion,there is an obvious crack closure effect in the crack propagation stage under spray corrosion condition,resulting in a lowerΔK stage that the crack growth rate of the spray condition is lower than that of the pure fatigue condition;for the lower pH value of corrosive liquid,the crack growth rate curve becomes steeper but its initial rate is also lower;in the aspect of stress ratio,increasing the stress ratio can obviously alleviate the crack closure effect,and the crack growth rate increases with the increase of the stress ratio.

关 键 词：Q420B 酸雨环境 腐蚀疲劳裂纹扩展 断口分析 P-da/dN-ΔK概率模型 

分 类 号：TU312[建筑科学—结构工程]