Effective permittivity of air-filled cracks in piezoelectric ceramics due to crack bridging
Effective permittivity of air-filled cracks in piezoelectric ceramics due to crack bridging
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DOI：
10.1016/j.actamat.2012.10.006
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发表时间：
2013-02
期刊：
影响因子：
9.4
通讯作者：
P. Neumeister;M. Jurisch;H. Jelitto;A. Engert;G. Schneider;H. Balke
中科院分区：
文献类型：
--
作者：
P. Neumeister;M. Jurisch;H. Jelitto;A. Engert;G. Schneider;H. Balke
非导电的，充满空气的压电陶瓷裂纹的断裂力学调查需要的知识的裂纹间隙的电渗透性。众所周知，从实验中，该电渗透率是显着大于一个充满空气的间隙与光滑面的电渗透率考虑在常见的裂纹模型。本文通过研究裂纹桥接对压电陶瓷非导电充气裂纹磁导率的影响来评估这种现象的起源。裂纹桥接区域的识别和量化的裂纹表面形貌的裂纹在软PZT陶瓷PIC 151，这是通过光学3-D显微镜测量后，总故障的试样。基于一个简单的均匀化方法，现实的陶瓷面间隙系统的介电性能量化的有效介电常数的假设介质在一个理想化的裂纹具有相同的裂纹开口和光滑的面孔。的有效介电常数推导出的裂纹开口的函数，这增加在小裂纹开口的裂纹开口增加。对于PIC 151，计算的最大有效介电常数是空气介电常数的46倍。尽管简化和假设内所提出的模型，在PZT陶瓷Vibrit 1100的压痕裂纹的预测和测量的电位降之间的比较显示出整体良好的协议。总之，本文提供的证据表明，裂纹桥接确实是这种裂纹的导电性增加的原因。
Fracture mechanical investigations of non-conducting, air-filled cracks in piezoelectric ceramics require knowledge of the electrical permeability of the crack gap. It is well known from experiments that this electrical permeability is significantly greater than the electrical permeability of an air-filled gap with smooth faces as considered in common crack models. The present paper assesses the origin of this phenomenon by investigating the effect of crack bridging on the electrical permeability of non-conducting air-filled cracks in piezoelectric ceramics. Regions of crack bridging are identified and quantified from the crack face topography of a crack in the soft PZT ceramic PIC151, which was measured by optical 3-D microscopy after total failure of the specimen. Based on a simple homogenization approach, the dielectric properties of the realistic ceramic face gap system are quantified by means of the effective permittivity of a hypothetical medium in an idealized crack with the same crack opening and smooth faces. The effective permittivity derives to a function of the crack opening, which increases with increasing crack opening at small crack openings. For PIC151, the computed maximum effective permittivity is 46 times the permittivity of air. Despite the simplifications and assumptions adopted within the proposed model, the comparison between the predicted and measured electric potential drop across an indentation crack in the PZT ceramic Vibrit1100 reveals an overall good agreement. In conclusion, the paper provides evidence that crack bridging is indeed the reason for the increased electrical permeability of such cracks.