兰州大学机构库 >土木工程与力学学院
超磁致伸缩材料的本构理论研究
Alternative TitleThe Study of Constitutive Theory for Giant Magnetostrictive Materials
孙乐
Thesis Advisor郑晓静
2007-04-02
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name博士
Keyword超磁致伸缩材料 力-磁-热多场耦合 磁滞效应 非线性 饱和回线 小回线 外斯分子场 钉扎效应 有效磁场 体积分数 经典损耗 反常损耗 畴转 壁移
Abstract

超磁致伸缩材料作为一种新型的功能材料具有很多优越性,目前人们已经设计并制造出各种智能结构和器件,如:主动减振装置、高精度线性马达、超磁致伸缩微泵、微阀门、微定位装置等等,使得磁致伸缩材料在众多的功能材料中备受瞩目。然而实验表明超磁致伸缩材料的本构行为具有十分复杂的非线性特征包括饱和现象、力-磁-热多场耦合效应及磁滞效应,对此认识不清将严重影响以此材料为核心原件的众多功能器件的设计和使用。为此,本文针对超磁致伸缩材料的复杂本构行为,用不同的方法 (热力学或磁畴理论或二者相结合),从不同的角度 (可逆和不可逆磁化过程),在不同的适用条件 (外加静磁场或交变磁场)下对超磁致伸缩材料复杂的非线性本构行为进行了理论建模,这一理论研究既涵盖了超磁致伸缩材料的宏观多场耦合效应及磁滞现象,又能从微观机理上揭示其物理本质,补充和完善了现有超磁致伸缩材料的本构理论。

首先,从宏观连续介质力学的角度,将超磁致伸缩材料弹性Gibbs自由能G(σ,M,T)进行泰勒展开,运用热力学关系导出了一个针对一维超磁致伸缩材料的能全面描述力-磁-热耦合行为的非线性宏观唯象的理想(无磁滞)本构模型。在已有力-磁耦合模型的基础上该模型不仅涉及了通常的热应力导致的应变还涉及了由于热扰动产生的热磁耦合应变;其次,在考虑自发磁化磁矩间的相互作用能的基础上重新推导内能及弹性 Gibbs 自由能的表达式,运用热力学关系导出一个涉及力-磁-热多场耦合效应和“外斯分子场”的有效磁场,并在此基础上考虑可逆磁化,引入钉匝效应引起的磁滞损耗、高频激励引起的经典损耗和反常损耗,建立了一个适用于静、动态加载条件下的超磁致伸缩材料多场耦合磁滞模型。同时引入“体积分数”对此耦合磁滞模型做出修正,使其模拟的次要回线能够满足“封闭性”;最后,针对现有物理模型的不足,从基本的磁畴理论出发,全面考虑磁畴运动的两个主要形式——畴转和壁移在外加预压力和磁场作用下对磁化过程的贡献,建立了超磁致伸缩材料的一维细观模型。与已有模型相比,上述理论模型能够从定性或定量两个方面更好的反映实验揭示的材料的力-磁-热多场耦合效应,磁滞效应以及各种微观参量对材料磁性能的影响。

总之,通过本文的工作,完善了现有的超磁致伸缩材料的本构理论研究,为更加深入地探讨以此类材料为主要元件的智能器件的设计、使用及控制问题奠定了一定的基础。

Other Abstract

Giant magnetostrictive material (GMM)is a kind of new type of functional material, which exhibits many outstanding advantages and has been used to design and fabricate many intelligent devices such as active vibration absorbers, linear motors, micro-pumps, micro-valves, and micro-positioners etc. However, many experiments show that there is nonlinear property of magnetic-elastic-thermal coupling and hysteresis inherent to giant magnetostrictive materials and it is difficult to design and control the corresponding giant magnetostrictive actuators in application.In the paper, a general theoretical study incorporating magnetic-elastic-thermal coupling and hysteresis is developed by thermodynamic relations or magnetic domain theory or combining both of them. The constitutive study can clarify the micromechanism of the complicated properties of giant magnetostrictive materials.Furthermore, it can describe macroscopic constitutive behavior of the materials under dc and ac magnetic field.

Firstly, a nonlinear unhysteresis constitutive model to describe magnetic-elastic-thermal coupling property is suggested in this paper. The model considered here is built on the Gibbs free energy function  and thermodynamic relations are used to obtain the constitutive expressions. Based on the previous magnetic-elastic model , both thermal strain and strain due to thermal-magnetic coupled are considered.Secondly,a hysteresis model for giant magnetostrictive materials is deduced by considering the hysteresis loss,the classical loss and the excess loss. Here the energy contribution from magnetic interaction among domains is incorporated to the Gibbs free energy function, thus the effect field of the hysteresis model involves the contribution of magnetic-elastic-thermal coupling and the Weiss molecular field. Thus the model can describe coupled hysteresis behavior of the materials under dc and ac field. In order to ensure closure of minor loop, the “volume fraction” for magnetization is considered in the model. Finally, a Meso- physical model for giant magnetostrictive materials is derived from magnetic domain theory and it involves the contribution of the domain rotation and the domain wall motion to magnetization under the pre-pressure and magnetic field. In the model,the  micromechanism mechanics of the complicated propertie of giant magnetostrictive materials are clarified. Results based on above theoretical studies show that the nonlinear properties of giant magnetostrictive materials, such as the magnetic-elastic-thermal coupling and hysteresis effect, are in excellent agreement with experimental data in quality or in quantify. Furthermore the theoretical results can describe the effect of micro-parameter, such as inclusion, internal stress and domain size etc., on the magnetic properties well.

Sumary, a general theoretical study about constitutive behavior of the giant magnetostrictive materials is developed, and the further study on the design,application and control of the corresponding actuators problems can be carried out based on the work.

URL查看原文
Language中文
Document Type学位论文
Identifierhttps://ir.lzu.edu.cn/handle/262010/226679
Collection土木工程与力学学院
Recommended Citation
GB/T 7714
孙乐. 超磁致伸缩材料的本构理论研究[D]. 兰州. 兰州大学,2007.
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