Numerical investigation of crack propagation direction in ferroelectric actuators
Numerical investigation of crack propagation direction in ferroelectric actuators
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DOI：
10.1117/12.2258229
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发表时间：
2017-04
期刊：
影响因子：
--
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
智能结构和微机电系统的功能，例如铁电多层致动器（MLA）、粗纤维复合材料等，本质上会受到裂纹形成的影响。在当前的研究中，PZT MLA 中可能的裂纹模式是通过有限元方法 (FEM) 进行数值模拟的。全耦合机电有限元分析用于研究极化过程中以及后续使用中机电负载下的 MLA 行为。铁电用户元件是为商业软件 ABAQUS 开发的，用于模拟微机械非线性散装材料行为。它们可以真实地模拟由于四方畴切换而导致的铁电陶瓷的极化过程。由实验可知，裂纹主要起源于电极尖端，然后沿着电极界面扩展。在 MLA 中还观察到斜裂纹和交叉裂纹。在许多情况下，出现的裂纹的类型和方向取决于边界条件的共烧、非共烧或部分共烧模型。最初，研究沿电极平面的不同位置处的最大切向应力的方向。然后，垂直于最大切向应力作用方向将机电粘合元件 (EMCZE) 插入体铁电元件之间。 CZE 中的损坏按照牵引分离定律累积。通过模拟，发现并研究了具有共烧、非共烧或部分共烧陶瓷层的 MLA 中裂纹扩展的不同模式。数值结果与实验观察结果一致，有助于更好地理解智能结构中发生的复杂多物理过程。
The functionality of smart structures and microelectromechanical systems, such as ferroelectric multilayer ac- tuators (MLA), macro-fiber composites, etc., can be essentially influenced by crack formation. In the current research possible cracking patterns in PZT MLAs are numerically modeled by finite element method (FEM). Fully coupled electro-mechanical FE analysis is used to investigate the MLA behavior during poling process and under subsequent in-service electromechanical loading. Ferroelectric user elements are developed for commercial software ABAQUS to mimic micromechanical non-linear bulk material behavior. They allow to simulate realisti- cally the poling process of ferroelectric ceramics as a result of tetragonal domain switching. It is known from the experiments, that cracks mainly originate from an electrode tip and then propagate along the electrode interface. There are as well oblique cracks and cross-cracks observed in MLAs. In many cases the type and direction of emerging cracks depend on cofired, non-cofired or partially cofired model of boundary conditions. Initially, the direction of maximum tangential stresses is studied at different positions along the electrode plane. Then electromechanical cohesive elements (EMCZE) are inserted between the bulk ferroelectric elements perpendicular to the direction of action of the maximum tangential stresses. Damage in the CZE is accumulated in accordance with the traction-separation law. As a result of the simulations different patterns of crack propagation in MLAs with cofired, non-cofired or partially cofired ceramics layers are found and studied. The numerical results co- incide with the experimental observations and lead to a better understanding of the complicated multi-physics processes taking place in smart structures.