Simulation of fatigue damage in ferroelectric polycrystals under mechanical/electrical loading
Simulation of fatigue damage in ferroelectric polycrystals under mechanical/electrical loading
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DOI：
10.1016/j.jmps.2018.03.013
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发表时间：
2018-03
影响因子：
5.3
通讯作者：
S. Kozinov;M. Kuna
中科院分区：
文献类型：
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作者：
S. Kozinov;M. Kuna
由铁电陶瓷制成的智能结构的可靠性由于在外部电和/或机械载荷的作用下形成裂纹而显著降低。本文提出了一个铁电介观结构低周疲劳的数值模型。在有限元模拟中，利用两个用户单元例程的组合。第一个是用来模拟晶粒内的微机械铁电畴开关行为。第二种是基于机电循环牵引分离定律（TSL）的内聚区模型（EMCCZM）模拟晶界疲劳损伤。为了进行数值模拟，陶瓷颗粒结构的扫描电子显微镜图像被数字化和网格化。系统地分析了这种细观结构对循环电载荷或机械载荷的响应。模拟结果得到了晶粒内部的电势、电场、位移和极化分布，以及晶粒内部的机械应力和变形。在晶界处，分析了损伤的形成和演变，直到最终失效并引起介电常数的退化。结果表明，该模型能正确模拟铁电多晶在极化过程中的行为和循环加载下的渐进损伤，是第一个同时考虑畴重取向和晶界断裂内聚模拟的铁电多晶模型和数值分析。这有助于理解铁电体在疲劳过程中的失效机理。
The reliability of smart-structures made of ferroelectric ceramics is essentially reduced by the formation of cracks under the action of external electrical and/or mechanical loading. In the current research a numerical model for low-cycle fatigue in ferroelectric mesostructures is proposed. In the finite element simulations a combination of two user element routines is utilized. The first one is used to model a micromechanical ferroelectric domain switching behavior inside the grains. The second one is used to simulate fatigue damage of grain boundaries by a cohesive zone model (EMCCZM) based on an electromechanical cyclic traction–separation law (TSL). For numerical simulations a scanning electron microscope image of the ceramic’s grain structure was digitalized and meshed. The response of this mesostructure to cyclic electrical or mechanical loading is systematically analyzed. As a result of the simulations, the distribution of electric potential, field, displacement and polarization as well as mechanical stresses and deformations inside the grains are obtained. At the grain boundaries, the formation and evolution of damage are analyzed until final failure and induced degradation of electric permittivity. It is found that the proposed model correctly mimics polycrystalline behavior during poling processes and progressive damage under cyclic electromechanical loading.To the authors’ knowledge, it is the first model and numerical analysis of ferroelectric polycrystals taking into account both domain reorientation and cohesive modeling of intergranular fracture. It can help to understand failure mechanisms taking place in ferroelectrics during fatigue processes.