Microcrack damage and nonlinear constitutive behavior of ferroelectric materials - a mesomechanical approach

在铁电材料中，由于足够高的电载荷或机械载荷，会产生伴随域切换的微裂纹。它也出现在相对较低的负荷水平在循环电气负荷。微裂纹的形核、生长和聚结不仅会导致材料的电疲劳、机械疲劳和宏观开裂，而且会降低材料在服役初期的有效性能。该项目的目的是建立基于细观力学的宏观本构关系，考虑到区域切换和微裂纹作为相互作用机制。该分析是基于对具有单个成核微裂纹的铁电多畴单元胞的研究。采用解析法和有限元法对电加载和电卸载过程的详细机电性能进行了研究。对于中宏观过渡，采用了Rice的内变量概念和微裂纹扩展理论（DMG）域。理论结果将与文献中典型构型的实验结果进行比较。

Microcracking accompanied with domain switching occurs in ferroelectric materials as a result of sufficiently high electric or mechanical loading. It also appears at relatively low load level during cyclic electrical loading. Nucleation, growth and coalescence of microcracks may not only lead to electric and mechanical fatigue and macroscopic cracking, but also degrade the effective properties of materials in the early stage of service. It is the aim of the project to establish a mesomechanically based macroscopic constitutive relation, taking into account domain switching and microcracking as interacting mechanisms. The analysis is based on the investigation of a ferroelectric multidomain unit cell with a single nucleating microcrack. The detailed electromechanical behaviour during electric loading and unloading is studied by analytical methods and numerically by the finite element method. For the meso-to-macro transition, Rice's concept of internal variables and the domain of microcrack growth theory (DMG) are used. The results of the theory will be compared with experimental findings from the literature for typical configurations.