Multi-scale modeling of fracture behavior of polycrystalline ferroelectric ceramics under monotonic and cyclic electromechanical loading

单调和循环机电载荷下多晶铁电陶瓷断裂行为的多尺度建模

基本信息

批准号：
327013632
负责人：
Professor Dr. Meinhard Kuna
金额：
--
依托单位：
Institut für Mechanik und Fluiddynamik
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2017
资助国家：
德国
起止时间：
2016-12-31 至 2020-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/327013632?language=en
关键词：
Multi scale modeling fracture behavior

项目摘要

Nowadays, functional ferroelectric ceramics are widespread applied in engineering as sensors, actuators, or integrated component of smart composites, where they are exposed to coupled electrical and mechanical in-service loads. Because of their brittleness, cracks can be formed and propagate at material defects and local stress concentrations, which impairs the strength, life time and reliability of such devices. This project is aiming at investigating the fracture processes in ferroelectric materials and devices under electrical, mechanical and combined loading. The loading may happen monotonic or cyclic, which leads either to brittle fracture or to fatigue damage. A multi-scale approach is developed to model the material behavior of polycrystalline ferroelectric ceramics, which comprises the domain processes on the micro-scale and the non-linear electromechanical continuum laws on the macro-scale. These models are implemented in a finite element method. Cyclic electromechanical cohesive zone elements are used to simulate failure phenomena like damage, crack formation and crack growth.By means of these models, the electromechanical stress situation at cracks is investigated in order to find suitable fracture mechanical parameters and failure criteria. At the macro-scale, the configurational force concept is favored. At the micro-scale, the discrete microstructure of the polycrystal is reproduced to model the fracture process zone. This approach allows to correlate the properties of the process zone with the macroscopically measureable fracture toughness and crack parameters. The focus lies on the influence of the electric field on the loading situation and fracture toughness.As a result of the project, a simulation tool will be developed, which enables a scale-bridging quantitative description of the elementary failure processes, crack initiation and crack propagation of ferroelectric ceramics.Finally, the elaborated models are verified by comparison with available fracture experiments. They are exemplarily applied to selected ferroelectric devices such as multi-layer stack actuators or macro-fiber-composites.

如今，功能性铁电陶瓷作为传感器、执行器或智能复合材料的集成组件广泛应用于工程中，在使用中它们承受着耦合的电气和机械负载。由于其脆性，裂纹可能在材料缺陷和局部应力集中处形成并扩展，从而损害此类设备的强度、使用寿命和可靠性。该项目旨在研究铁电材料和器件在电气、机械和组合载荷下的断裂过程。载荷可能单调或循环发生，从而导致脆性断裂或疲劳损坏。开发了一种多尺度方法来模拟多晶铁电陶瓷的材料行为，其中包括微观尺度上的域过程和宏观尺度上的非线性机电连续体定律。这些模型是通过有限元方法实现的。循环机电内聚区单元用于模拟损伤、裂纹形成和裂纹扩展等失效现象。通过这些模型，研究裂纹处的机电应力情况，以找到合适的断裂力学参数和失效准则。在宏观尺度上，构形力概念受到青睐。在微观尺度上，再现多晶的离散微观结构以模拟断裂过程区。这种方法可以将加工区域的特性与宏观可测量的断裂韧性和裂纹参数相关联。重点在于电场对加载情况和断裂韧性的影响。该项目的结果是，将开发一种模拟工具，能够对基本失效过程、裂纹萌生和裂纹进行尺度桥接的定量描述最后，通过与现有的断裂实验进行比较，验证了精心设计的模型。它们典型地应用于选定的铁电器件，例如多层堆栈致动器或粗纤维复合材料。