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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.

目前，功能铁电陶瓷作为传感器、执行器或智能复合材料的集成元件在工程中得到了广泛的应用。由于它们的脆性，裂纹可能在材料缺陷和局部应力集中处形成和传播，这损害了这种装置的强度、寿命和可靠性。本计画旨在研究铁电材料与元件在电、力及复合载荷下的断裂过程。加载可以是单调的或循环的，这将导致脆性断裂或疲劳损伤。发展了一种多尺度方法来模拟多晶铁电陶瓷的材料行为，该方法包括微观尺度上的畴过程和宏观尺度上的非线性机电连续律。这些模型是在一个有限元方法。采用循环机电内聚区单元模拟损伤、裂纹形成和扩展等破坏现象，研究裂纹处的机电应力状态，以寻找合适的断裂力学参数和破坏准则。在宏观尺度上，构型力的概念是有利的。在微观尺度上，再现了多晶体的离散微观结构，模拟了断裂过程区。该方法允许将处理区的性质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。作为该项目的结果，将开发一个模拟工具，它能够定量描述铁电陶瓷的基本失效过程，裂纹萌生和裂纹扩展。最后，通过与现有断裂实验的比较，验证了详细的模型。它们示例性地应用于选定的铁电器件，例如多层堆叠致动器或宏纤维复合材料。