【作者】 黄莉；

【导师】 李卓球；

【作者基本信息】 武汉理工大学 ， 结构工程， 2005， 博士

【摘要】 本论文的研究课题来源于国家自然科学基金重点项目——机敏混凝土及其结构(项目编号:50238040)。 大型水坝、桥梁、核电站安全壳等重大混凝土工程的安全可靠性、耐久性问题是涉及国家经济发展与国家安全的重大问题。而已有的混凝土大型结构和基础设施的损伤积累和灾变行为日趋突出。因此,对重大混凝土工程结构进行损伤监测与分析已成为土木工程领域中的重要研究课题之一。 本文提出了利用碳纤维混凝土的功能特性,对混凝土中的损伤进行红外检测的方法,并从实验、理论、数值计算等多方面对检测机理、影响因素等进行了分析。同时对将此方法应用于实时监测时所产生的力、电、热耦合问题进行了一定的分析与研究。主要成果与创新之处如下: 1、利用碳纤维混凝土的功能特性,提出并设计了基于电热的碳纤维混凝土红外热像检测方法,并通过实验研究证实了方法的可行性,检测结果显示只需通低压电源就能使远离缺陷的正常部位温度升高1～2℃,而在缺陷附近的表面处温度大幅度上升,因此比一般红外检测方法更利于缺陷的检出。同时,检测结果也显示了检测与时间、材料组分、缺陷形态的相关性。 2、建立了碳纤维混凝土红外热像方法的瞬态热传导温度分析模型,研究分析了材料组分及外部环境因素从材料电、热性能参数方面对检测的影响机理,以及检测的主导机制:宏观缺陷的存在和缺陷局部微观特性导致的非均匀内热源效应,并采用等效电阻串、并联模型对其进行了解释。 3、建立了基于碳纤维混凝土红外热像方法的碳纤维混凝土缺陷体电-热耦合有限元分析模型,利用大型有限元软件Marc及自编用户子程序进行了数值计算,将所得结果与实验结果进行模拟与比较,进一步验证了检测方法的可行性和有限元数值模拟的有效性。同时,大量的数值结果分析显示了此种红外检测方法的敏感因素,为具体检测方案的选择和优化提供了依据。 4、研究了利用格林函数法求解缺陷体电、热耦合问题温度场的方法。在分析了不同缺陷情况下电场分布的基础上,利用瞬态热传导格林函数法求解得到二维缺陷体温度场的近似理论解,编程计算的结果显示了所求温度分布与实测更多还原

【Abstract】 This dissertation was supported by the Key Project ’smart concrete and structures’ of National Science foundation under grants No. 50238040.The safety, reliability and durability of large concrete project, including large dam, bridge, containment vessel of nuclear power station and etc., are momentous problems relating to national economic development and national safety. However, the problems of accumulation damages and catastrophic behavior of the in being larger concrete structures and national infrastructure become very prominent. Therefore, study on monitoring and analyzing the damage of momentous concrete structures is one of the important research subjects in civil engineering.A nondestructive detection method with infrared imaging is presented by making use of the functional property of carbon fiber-reinforced concrete (CFRC). Its detection mechanism and influencing factors are analyzed with experiments, theory, and numerical analyses. Meanwhile, studies have been made to some degree on the coupling problems of force, electricity and heat potentially in real-time monitoring. The main research works and innovations of this paper are as follows:Firstly, an improved infrared imaging method is proposed and designed to detect the damage of concrete by using of the functional properties of electro-thermal carbon fiber-reinforced concrete. The feasibility of the method is verified by experiments. The detection results show that under lower DC voltage the temperature of normal areas far from defects is able to rise 1~2°C in specimen, however, the surface temperature near the defects rises greatly. Thus, it makes the infrared imaging method more powerful to inspect the defects out. At the same time, it shows that the detection results are related to the inspection time, material components and defect shape.Secondly, model for analyzing the temperature of this transient heat transfer application is constructed based on the improved infrared imaging detection method. The mechanisms influencing on the detection from the material components and the surrounding environment are studied in terms of the electrical and heat parameters of the material. The existence of macro defects and the micro characteristic of local area near the defects, which lead to the effect of inhomogeneous internal heat source, are also studied as the leading mechanism to the detection.Thirdly, the MARC finite element analysis software and subroutine program is used to analyze the model of the Joule’s heating problem for the defective CFRC specimen. By comparing the numerical results with the experimental results, the feasibility of this method and the validity of the finite element simulation are verified. At the same time, large quantity of numerical results reveals the sensitivity factors of this detection method. The study provides reference for selecting and optimizing the detection scheme in practice.Fourthly, the theoretical solution with Green’s function is developed to solve theJoule’s heating problem and get the temperature field in the defective specimen. On the basis of analyzing the electrical field in the defective bodies with different defect shape, two-dimensional temperature field is obtained by using the Green’s function solution. The computation results by programming indicate that the distribution of temperature is the same as that of actual measurement. And the mechanism of this defection is further disclosed in theory.Fifthly, microscopic mechanism of the coupling phenomenon of force, electricity and heat, which appears in real-time monitoring, is analyzed. For the situation of simply loading, the variation of effective load area is applied to describe the damage in specimen, which can reflect not only the variation of mechanical property of material, but also the variation of electrical parameter. With the damage variable in terms of effective load area, the evolvement law of electrical parameter with the damage of CFRC is established under compression load. Combining with the corresponding Mazars damage mechanical model and energy equation, the temperature field for odd coupling problem of force and electricity, electricity and heat is obtained.The study involves several science areas such as mechanics, electricity, concrete material science, heat transfer and so on. The production has significant meanings in improving the efficiency and precision of infrared nondestructive detection in concrete, and enhancing its application in the concrete construct. Moreover, it has certain guiding effect to the realization of real-time damage monitoring and the application of CFRC in key civil engineering structures.更多还原