【作者】 陈雨；

【导师】 文玉梅；

【作者基本信息】 重庆大学 ， 仪器科学与技术， 2006， 博士

【摘要】 在前期研究工作中提出的压电机敏土木工程结构系统的基础上,针对实际的土木工程中混凝土结构的健康监测,设计了一种旨在进行混凝土应力及温度监测的压电机敏混凝土模块。并对这种压电机敏模块的多种物理特性进行了系统的理论及实验研究。研究结果为实现利用该压电机敏结构进行土木工程结构的健康监测应用奠定了基础。主要的研究内容是围绕着压电机敏混凝土模块中所涉及的三个对象,即混凝土结构、PZT压电陶瓷以及二者相互耦合形成的混凝土-压电敏感单元结构进行的。研究的主要目的是通过对各研究对象的独立及相互耦合特性的研究,通过理论分析和实验验证,来证明所提出的压电机敏模块用于土木工程结构应力及温度监测的可行性,并解释监测中所涉及的监测原理和技术要点。所取得的研究成果包括以下几点:(1)系统地归纳和总结了混凝土材料的常规物理特性,分析了在相应环境中本课题所涉及的压电敏感元件及其同混凝土材料间由于相互耦合而存在的物理特性,并提出了一种能够同时实现混凝土结构中应力及温度监测的PZT压电陶瓷埋入式混凝土机敏模块。(2)通过引入复电弹常数的方法,建立了埋入混凝土中压电敏感单元的等效电路模型。根据唯象理论及晶畴理论,分析了压电敏感元件在埋入状态下的各种能量损失特性。提出了一种通过测量压电等效电路参数来计算能够反映能量损失的耗散因子的方法。该方法不用测量复电弹常数中的实部和虚部,便可直接计算出三种耗散因子的值,避免了测量复电弹常数时要求测量多种振动模式下的多个参数值进行迭代计算的过程。该方法是基于的是压电材料单一振动模式下的等效电路模型,推导的耗散因子计算式相对于压电元件的振动模式是相互独立的,即不同振动模式下的耗散因子只同该模式下的等效电路参数有关。(3)设计了一种适用于埋入混凝土的PZT压电陶瓷敏感单元结构。该结构通过在圆片形PZT压电陶瓷上覆盖适当厚度和硬度的橡胶层材料,缓解了PZT陶瓷由于埋入混凝土中受到的一些不利影响,包括a)解决了压电陶瓷裸露电极间在含水混凝土中的电绝缘问题,b)缓解了混凝土凝固过程中由于体积收缩在压电陶瓷上产生的应力积累及应力集中,c)减小了由于混凝土粗糙骨料在压电陶瓷上产生的应力集中,d)保护了PZT陶瓷,并防止了电极上的银电镀层受到混凝土材料的破坏。(4)研究了混凝土凝固过程中,埋入的PZT压电陶瓷元件受到混凝土干缩作用时的应力响应特性。研究表明,混凝土干缩过程中产生的应力将直接施加在压更多还原

【Abstract】 Based on the proposed piezoelectric sensitive structure system for the civil engineering, a piezoelectric-embedded concrete element is designed to measure the stress and temperature of the concrete structure. Three objects are concerned in the research: the concrete, the piezoelectric ceramic, and the coupling structures of them. The theoretical analysis and experimental researches are conducted to prove the feasibility of the proposed method, and explain the technical points and the measuring principle. The contributions of this paper are listed as follows:(1) According to the basic knowledge and principle in the concrete engineering, the features and behaviors related to both the concrete material and the embedded piezoelectric ceramic are disscused. Then, a concrete smart element with an embedded piezoelectric ceramic is designed.(2) The equivalent circuit for the embedded piezoelectric ceramic is established. The complex material coefficients are introduced in the equivalent circuit to describe the energy losses occuring in the embedded piezoelectric materials. The loss mechanism is explained by the theories of the domain wall (motion) and the crystal defect. A novel method is proposed to obtain the dissipation factors of piezoelectric materials. Instead of the traditional iterative method in which measuring parameters of the different viberation modes are demanded, we suggest that the dissipation factors are evaluated by the equivalent circuit parameters of the specific viberation mode.(3) A structure is designed for the piezoelectric ceramic to be embedded in the concrete. A layer of rubber is covered on either side of the piezoelectric ceramic plate. The material and the thickness of the rubber layer are also determined. The use of the rubber layer solves the problems of the piezoelectric ceramic being embedded, including a) the electrical insulation in the concrete containing water, b) the stress accumulation on the embedded piezoelectric ceramic produced by the shrink of the concrete volume in the concretion, c) the stress concentration caused by the aggregate in the concrete materials, d) the damage on the electrodes of the piezoelectric ceramic induced by the concrete.(4) The stress responses of the embedded piezoelectric ceramic in the concretion are researched. It is found that the stress caused by the volume shrinkage will be applied on the ceramic directly, and will cause the changes of the physical characteristics of the更多还原