层状复合磁电材料的弹性动力学研究

发布时间：2018-01-06 14:38

本文关键词：层状复合磁电材料的弹性动力学研究　出处：《南京师范大学》2015年博士论文　论文类型：学位论文

【摘要】：磁电效应是指电致变磁有序或磁致变极化序。磁电效应可以实现磁、电能量之间的相互转换和调控,在信息存储、磁电传感及高能电子传输等器件小型化方面具有广泛的应用前景。由于天然的磁电材料稀少且缺乏实用性,因此各类复合磁电材料成为目前主要的研究对象。迄今,磁电转换效率的实际测量值总是小于理论预期。为解决此一偏差,本论文选用2-2型TDF-PZT层状复合磁电材料,从材料的非均匀应力和应变入手,依据弹性力学理论,研究了复合块体材料中铁磁体磁致伸缩导致的界面应力,以及该界面应力通过弹性耦合所诱导的铁电体内的应力分布,并在此应力的基础上取得了与实验结果较为一致的磁电效应理论模型。具体研究内容如下：1、选用主流的层状复合磁电材料,以Harshe、Bichurin、南策文、Dong等学者的理论模型为主要依据,分析了“乘积效应”下各类双层复合材料在不同磁场模式下的磁电效应规律,回顾了这一结构的磁电效应的理论值总大于实验结果的现象,分析了为弥合这一差距而引进的界面耦合系数方法的利弊,并引出本文研究的重点——圣维南原理和弯曲引起的压电相中应力及应变的非均匀分布。2、测量了双层复合材料自由端的应变,发现压电材料自由端的应变幅度随压电材料本身厚度的增大而减小,根据圣维南原理的局部作用效应,从弹性力学的平面问题出发,针对磁电耦合中磁致伸缩相诱导的界面应力,寻找出一组合理的边界条件,推导出压电相的内应力分布,并根据此应力分布修正了原有的磁电效应理论模型。较之已有模型,新模型给出的理论数值与实验结果符合得更好,从而证实了考虑圣维南原理的必要性。在局部作用原理的影响下,压电材料内部的应力分布随厚度的增加逐渐减小,导致整体压电效应的减弱。3、根据压电材料的蝴蝶状应变,证实了双层复合材料中的铁电相在外加磁场下其内应力呈非均匀分布的假设。根据弹性力学中构件弯曲的理论模型,针对弯曲这一典型的非均匀应变现象,推导出磁场下复合材料弯曲时的弯曲角度与磁场及材料形状、杨氏模量之间的关系,理论模拟与实验匹配良好。同时依据电致伸缩方程理论,成功模拟出复合材料应变时的蝶状图形。
[Abstract]:Magnetoelectric effect refers to electromagnetically variable magnetic order or magnetically induced polarization order. Magnetoelectric effect can realize the mutual conversion and regulation of magnetic and electric energy in the storage of information. The miniaturization of magnetoelectric sensing and high-energy electron transmission has a wide range of applications due to the scarcity of natural magnetoelectric materials and the lack of practicability. So all kinds of composite magnetoelectric materials have become the main research object. Up to now, the actual measurement value of magnetoelectric conversion efficiency is always smaller than the theoretical expectation. In this paper, 2-2 TDF-PZT layered composite magnetoelectric material is selected, starting with the inhomogeneous stress and strain of the material, and based on the theory of elasticity. The interfacial stress induced by magnetostriction of ferromagnet in composite bulk materials and the stress distribution in ferroelectrics induced by elastic coupling are studied. On the basis of this stress, a theoretical model of magnetoelectric effect is obtained, which is consistent with the experimental results. The specific research contents are as follows: 1. The mainstream layered composite magnetoelectric material is selected to use Harshe. On the basis of the theoretical model of Bichurin, Nan Zi-wen Dong and other scholars, the magnetoelectric effects of all kinds of double-layer composite materials under the "product effect" under different magnetic field modes are analyzed. The phenomenon that the theoretical value of magnetoelectric effect of this structure is always larger than the experimental results is reviewed, and the advantages and disadvantages of the interfacial coupling coefficient method introduced to bridge the gap are analyzed. The stress and strain distribution in the piezoelectric phase caused by bending is also discussed. The strain at the free end of the double layer composite material is measured by using the Saint-Venant principle and the non-uniform distribution of the strain in the piezoelectric phase caused by bending. It is found that the strain amplitude at the free end of the piezoelectric material decreases with the increase of the thickness of the piezoelectric material itself. According to the local action effect of the Saint-Venant principle, the plane problem of elasticity is considered. Aiming at the interface stress induced by magnetostrictive phase in magnetoelectric coupling, a set of reasonable boundary conditions are found and the internal stress distribution of piezoelectric phase is deduced. According to the stress distribution, the original model of magnetoelectric effect is modified. Compared with the existing model, the theoretical value of the new model is in better agreement with the experimental results. Under the influence of the local action principle, the stress distribution in piezoelectric materials decreases with the increase of thickness, which leads to the weakening of the whole piezoelectric effect. According to the butterfly strain of piezoelectric material, the assumption that the internal stress of ferroelectric phase in the double-layer composite material is non-uniform distribution under the applied magnetic field is confirmed. According to the theoretical model of the bending of the member in elastic mechanics. Aiming at the typical inhomogeneous strain phenomenon, the relationship between bending angle, magnetic field, material shape, Young's modulus and bending angle of composite material under magnetic field is deduced. According to the theory of electrostrictive equation, the sphenoid pattern of composite strain was successfully simulated.
【学位授予单位】：南京师范大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TB33

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