【作者】 蒙彦宇；

【导师】 阎石；

【作者基本信息】 大连理工大学 ， 结构工程， 2013， 博士

【摘要】 随着土木工程结构日益向大型化、复杂化、智能化方向发展,混凝土结构健康监测与损伤识别的理论方法、试验研究及工程应用已经成为学术界的研究焦点。压电智能材料,如锆钛酸铅(Lead Zirconate Titanate,简称PZT)具有传感和驱动于一体的优越特性,其应用为重大工程结构和基础设施的长期健康监测与定性、定量的整体状态损伤识别技术提供了全新思路。通过实时有效地处理来自监测系统海量的不确定性的测量数据与信息,对结构的健康情况和损伤状态进行评价,可实现结构的服役状况监测,保证了结构的安全性、完整性、适用性和耐久性。基于上述背景,对压电智能骨料(传感器和驱动器)的力学模型、力学性能及其在混凝土结构健康监测与损伤识别中的应用等相关技术进行详细研究。具体工作包括以下几个方面：(1)给出了一种自行封装的压电智能骨料的制作工艺。针对压电智能材料与结构系统的特点,以混凝土基压电智能材料为传感和驱动元件,设计一种自行封装并与结构相容性良好的新型多功能“压电智能骨料(Piezoelectric Smart Aggregate)"作为传感器和驱动器使用。进一步改进和完善了其制作工艺和封装技术,有效地解决了传统压电材料相容性不好、耐久性差、具有易损性等方面的问题。建立了基于压电智能骨料列阵的智能结构健康监测体系与监测流程,为相应力学模型建立、力学性能分析、试验研究及其实际应用奠定了理论基础。(2)建立了压电传感器的力学模型,并进行了理论分析,数值计算与试验验证。基于PZT正压电效应的本构关系和结构动力学的振动原理,采用集总质量法,分别建立了粘贴式和埋入式PZT传感器的力学模型及数学模型；考虑粘结层阻尼效应,求解了传感器的振动方程及其电压表达式。通过简谐荷载激励下的数值模拟分析,确定了传感器力学与电学特性的对应关系,进一步明确了各个参数的影响规律；考虑不同胶层厚度和作用力影响,分别对粘贴和埋入式PZT传感器的传感性能进行试验研究,并与理论模型和数值分析结果相比较,验证了所建立的传感模型的正确性。(3)建立了压电驱动器的力学模型,并进行了理论分析,数值计算与试验验证。基于PZT逆压电效应的本构关系和结构动力学的振动原理,采用集总质量法,分别建立了单片PZT沿长度方向自由振动、粘贴式和埋入式PZT驱动力学模型；推导了PZT驱动运动方程并求解驱动力表达式；通过数值算例,考虑胶层等性能参数对驱动性能的影响,分析了驱动器输入信号与输出信号的关系、胶层性能及PZT尺寸对驱动力的影响；对粘贴和埋入式PZT驱动器的驱动性能分别进行试验研究,验证了驱动模型的合理性。(4)对压电智能骨料截面抗压与抗剪及冻融循环性能进行试验研究,揭示了压电智能骨料在抗压与抗剪及抗冻融环境下的服役性能。通过被动监测技术,研究压电智能骨料在不同应力作用下抵抗外荷载(抗压、抗剪)以及抗冻融循环的能力,分析了压电智能骨料自身受力性能和耐久性能。结果表明：压电智能骨料具有良好的抗压、抗剪及抗冻融循环的能力,能够满足使用功能的要求。从而使其在实际工程条件下能很好地保持力学性能的稳定性,确保与混凝土材料具有同样的服役寿命。(5)建立了基于小波分析的混凝土结构损伤统计指标和损伤程度、损伤概率及损伤位置判定方法,并提出了基于小波分析的压电智能骨料混凝土结构损伤统计识别算法。基于压电智能骨料的优越特性,将自行设计封装的压电智能骨料埋置在混凝土结构的指定位置,利用主动健康监测技术和压电波动理论,对混凝土结构的损伤情况进行实时在线监测及试验研究。建立了基于小波分析的混凝土结构损伤统计指标和损伤程度、损伤概率及损伤位置判定方法,并提出了基于小波分析的压电智能骨料混凝土结构损伤统计识别算法。试验结果证明了利用压电智骨料传感器和驱动器开展混凝土结构长期健康监测与损伤统计识别技术及其推广应用于实际工程的有效性和可行性。更多还原

【Abstract】 The theoretical method, experimental investigation and practical application of structural health monitoring (SHM) as well as damage identification (DI) have received considerable attentions in academic and engineering field along with the development of civil engineering structures into large scale, complicated and intelligent technology and the emergence of new smart materials. Piezoelectric smart materials, such as Lead Zirconate Titanate (PZT), play dual functions of both sensing and actuating and have many other distinct advantages. The application of PZT provides a new way for long-term SHM and qualitative and quantitative overall damage detection technology of significant engineering structures and infrastructures. Meanwhile, the convenient and practical SHM system and damage identification strategy based on PZT have implemented the status monitoring of structure service by real-time and effective processing of the vast amounts of uncertainty data and information from monitoring system. The structural health and damage status are evaluated to ensure the safety, completeness, applicability and durability of structures. Based on the above background, the author of this thesis ambitiously engaged in the research of the mechanical modeling of PZT smart aggregate (sensor and actuator), mechanical properties and its application in SHM and damage identification. The research work and innovations concerning theoretical analysis, numerical modeling and experimental research, are as follows:Firstly, the fabrication process of piezoelectric smart aggregates has been proposed. According to the characteristics of piezoelectric smart materials and structural systems, with the concrete-based PZT as sensing and actuating element, the new multifunctional piezoelectric smart aggregates working as transducers which have good compatibility with civil engineering structures and encapsulated in concrete block, are designed and developed, respectively. The fabrication process and encapsulation technique have been further improved and perfected. The serious problem affecting its application due to bad compatibility, poor durability and vulnerability of traditional PZT materials are effectively solved. The smart SHM system and monitoring processes based on PZT smart aggregate arrays are developed in order to lay a theoretical foundation for establishment of mechanical models, analysis of mechanical properties, experimental study and its application.Secondly, the mechanical model of piezoelectric smart sensor is built, the theoretical analysis, numerical simulation and experimental validation are performed, respectively. Based on direct piezoelectric effect and PZT constitutive relation as well as the vibration principle of structure dynamics, mechanical models of surface-bonded and embedded PZT sensors are simplified and established by employing the lumped-mass method. The vibration equation of PZT sensor is solved and the voltage expression is obtained in consideration of bonding layer damping effect. Numerical simulation analysis by using harmonic exciting load is implemented to determine the correspondence relation between the mechanical and electrical properties of PZT sensors, and the influence of different parameters is further defined. Considering different adhesive thickness and applying force, the experimental study on the sensing performance of surface-bonded and embedded PZT sensor is respectively carried out using the proposed models. The theoretical model and numerical results are compared with test results to verify the correctness of sensing model.Thirdly, the mechanical model of piezoelectric smart actuator is built, and theoretical research, numerical calculation and experimental validation are performed. According to the converse piezoelectric effect and PZT constitutive relation as well as the vibration principle of structure dynamics, the PZT actuating model is developed based on the free vibration along-length direction of monolithic PZT and the surface-bonded and embedded PZT by using lumped-mass method. The motion equation of PZT actuator and the expression of actuating force are derived and solved. The relationship between input signals and output signals of PZT actuator is analyzed by numerical examples. The influence of adhesive properties and the size on the PZT actuating force is concurrently studied. In view of the effect of different adhesive properties on PZT actuating force, the proposed surface-bonded and embedded models of PZT actuator and the impact on the adhesive layer of PZT actuating force are further validated by experiments. The experimental study on the driving performance of surface-bonded and embedded PZT actuator is respectively carried out using the proposed models. The experimental results match well with the theoretical analysis and the rationality of the actuator model is verified.Fourthly, the mechanical properties of PZT smart aggregates resisting to compression and shear failure and the freeze-thaw cycle are theoretically analyzed and experimentally studied. The service performances of PZT smart aggregates are revealed. The passive monitoring technology using the PZT-based transducers is employed to detect and analyze the performance of smart aggregates under different stress and the influence of the freeze-thaw cycle on smart aggregates for the purpose of more fully and intuitively understanding their durability and mechanical properties. The results show that PZT smart aggregate has good compression, shear and freezing-thawing resisting ability, and can satisfy the requirements of the use function, which make the smart aggregates well maintain the stability of mechanical properties and ensure the same service life to concrete material in practical engineering.Finally, the decision method of damage statistical index, damage degree, damage probability and damage location of concrete structure is established and the damage statistic identification algorithm for piezoelectric smart concrete structures is proposed based on wavelet analysis. Based on the superior characteristics of PZT smart aggregate sensor and actuator embedded in the designated position of concrete structure, the real-time online monitoring experimental research is conducted and an innovative method for damage detection is demonstrated by combing the active health monitoring technology-based PZT wave with the theory of probability and statistics and wavelet analysis as well as damage detection technology. The damage index-based wavelet analysis is effectively made and damage probability and degree-based statistics characteristics are developed to evaluate the damage states according to the attenuation of propagation wave. Furthermore, the rough damage location is effectively determined. The damage index-based wavelet analysis is also performed, the damage probability-based probability and statistics are proposed to convert uncertainty of damage detection into the mathematics description in context of probability and statistic. The proposed statistical algorithm of damage identification can effectively determine damage probability and damage degree, and provide a prediction for critical damage location of concrete structure. The research findings prove the tremendous effectiveness and feasibility of structural health comprehensive monitoring and damage detection technique in various large-scale concrete structures identification utilizing PZT transducers.更多还原