电循环载荷作用下铁电陶瓷裂纹尖端温升机理研究

Ferroelectric materials have been widely used in the fabrication of sensors, transducers and adaptive structures, on account of their intrinsic electromechanical properties and quick time response to external excitations. In these applications, ferroelectric ceramics may endure not only static combined mechanical and electrical loading, but also dynamic cyclic loads in application. Since they are very vulnerable to fracture and their static fracture toughness is low, the reliability concerns and optimal design of smart devices using ferroelectrics call for a better understanding of the fracture behavior. In the past decades, the theoretical and experimental fundamentals of linear static piezoelectric and ferroelectric fracture mechanics have been successfully established to date. In contrast to that, the fracture mechanics of piezoelectric and ferroelectric materials under dynamic cyclic electric loading is still an open topic and a challenge as well. Some important physical mechanisms responsible for material behavior are largely unexplored, such as the self-heating effects, rate-dependent effects and adiabatic effects around the crack tip. In this project, experimental and theoretical methods have been adopted to investigate the physical mechanisms. A systematic performance evaluation system for the ferroelectric materials under cyclic electric loading will be established. Experimental data will be obtained using the in-situ method. Models capturing the rate dependent, adiabatic around crack tip, self-heating, nonlinear, irreversible, high field, thermoelectro-mechanical behavior will be proposed. It is expected to obtain some innovative research results, which will give guidance for the design, manufacture and engineering application of ferroelectric devices.

铁电材料广泛应用于电子、激光、超声、水声、导航等领域，但由于断裂韧性低以及制备过程中微孔洞、裂纹等缺陷的产生，常导致铁电器件智能结构断裂破坏，其主要的失效问题来自循环交变电场。一些在力载荷或直流电载荷作用下不明显的问题，在动态电循环交变载荷服役环境下非常突出，如多次循环加载产生的自升温效应、动态快速加载产生的率效应、裂尖绝热效应等，将严重影响器件的使用寿命，而这方面的研究还不成熟。本项目通过实验和理论相结合的方法，拟建立铁电材料温升在位观测实验测量技术与表征方法，探讨同时考虑温升效应和率效应的铁电本构理论模型，提炼考虑裂纹尖端绝热温升效应的铁电断裂理论模型。期望在动态电循环载荷作用下铁电陶瓷断裂实验表征以及理论方面获得原创性成果，为交变电载荷作用下铁电器件设计、制备和工程应用方面提供指导。

铁电材料广泛应用于电子、激光、超声、水声、导航等领域，但由于断裂韧性低以及制备过程中微孔洞、裂纹等缺陷的产生，常导致铁电器件智能结构断裂破坏，其主要的失效问题来自循环交变电场，与力载荷和直流电场载荷相比，一些（准）静态载荷条件下不明显的问题，在动态电循环载荷服役环境下非常突出，如多次循环加载产生的自升温效应、动态快速加载产生的率效应、裂尖绝热效应等，将严重影响器件的使用寿命。本项目通过实验和理论相结合的方法，开展以下工作：.首先，实验测定不同电场加载频率、环境温度下的铁电块体材料的电滞回线，提出了考虑电场加载频率和温度效应的Johnson-Cook（J-C）型铁电畴变翻转准则； .其次，基于畴变致温升机理，提出了一种新型在位观测畴变实验表征方法，使得定量测定电致畴变热功转化系数、裂纹尖端180˚畴变区成为可能；率先报道了铁电陶瓷电致畴变电场做功未能全部转化为热能的实验结果，铁电陶瓷PZT-5材料热功转化系数约为80%，建立了经实验验证的铁电陶瓷热功转化的模型；.最后，展开循环电脉冲载荷作用下铁电陶瓷断裂力学研究。首次发现了循环低压高频电载荷作用下裂纹失稳扩展的新现象，提出了中心椭圆孔大范围畴变翻转理论模型（RLSS），发展了电/热/力多场耦合作用下裂纹扩展数值模拟方法，揭示了电/热/力多场耦合作用下铁电陶瓷裂纹失稳机理，建立了不同电场频率和幅值组合下的破坏相图，可指导压电/铁电器件工程设计；发展了主动电脉冲红外检测（AEPT）方法，可用于含缺陷压电/铁电器件的无损检测。