Measurement of the total energy release rate for cracks in PZT under combined mechanical and electrical loading
Measurement of the total energy release rate for cracks in PZT under combined mechanical and electrical loading
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DOI：
10.1115/1.2744027
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发表时间：
2007-11-01
影响因子：
2.6
通讯作者：
Schneider, G. A.
中科院分区：
文献类型：
--
作者：
Jelitto, H.;Felten, F.;Schneider, G. A.
在自制的控制裂纹扩展装置中，对平行于长轴的四点弯曲锆钛酸铅（PZT） v形缺口试样进行了断裂实验。在机械加载电场的基础上，在极化方向（即垂直于裂纹表面）平行和反平行施加高达500 V/min的电场。为了确定对总能量释放率的不同贡献，使用小信号调制/解调技术连续记录了样品的机械和压电顺应性以及电容。这允许计算机械，压电和电气部分的总能量释放率由于线性过程。在受控裂纹扩展过程中，这些线性贡献的总和归因于材料的固有韧性。总能量释放率的非线性部分主要与区域切换有关，导致裂纹尖端周围出现切换区。测量的力-位移曲线，结合调制技术，使我们能够确定这种机械非线性对PZT整体韧性的贡献。材料的固有韧性仅轻微依赖于外加电场（10%的影响），这可以通过裂纹内部的屏蔽电荷或电击穿来解释，由于非弹性过程的韧性部分从负电场增加到正电场，增加幅度高达100%。对于裂纹扩展过程中相应的非线性电能变化，只进行了粗略的估计。
Four-point-bending V-notched specimens of lead zirconate titanate (PZT) poled parallel to the long axis are fractured under conditions of controlled crack growth in a custommade device. In addition to the mechanical loading electric fields, up to 500 V/min are applied parallel and anti-parallel to the poling direction, i.e., perpendicular to the crack surface. To determine the different contributions to the total energy release rate, the mechanical and the piezoelectric compliance, as well as the electrical capacitance of the sample, are recorded continuously using small signal modulation/demodulation techniques. This allows for the calculation of the mechanical, the piezoelectric, and the electrical part of the total energy release rate due to linear processes. The sum of these linear contributions during controlled crack growth is attributed to the intrinsic toughness of the material. The nonlinear part of the total energy release rate is mostly associated to domain switching leading to a switching zone around the crack tip. The measured force-displacement curve, together with the modulation technique, enables us to determine this mechanical nonlinear contribution to the overall toughness of PZT The intrinsic material toughness is only slightly dependent on the applied electric field (10% effect), which can be explained by screening charges or electrical breakdown in the crack interior The part of the toughness due to inelastic processes increases from negative to positive electric fields by up to 100%. For the corresponding nonlinear electric energy change during crack growth, only a rough estimate is performed.