磁电弹性体中螺型位错与唇口裂纹的相互作用

研究磁电弹性体中螺型位错与唇口裂纹的相互作用。结合Muskhelishvili方法和干扰技术, 在假定裂纹面具有不可渗透条件下得到磁电弹性体中由位错和唇口裂纹所诱导的应力场、电场和磁场的解析解。应用广义Peach-Koehler公式,得到作用在位错上的影像力。通过数值算例,得到场强度因子的变化规律及影像力和广义力随位错位置的变化规律。     

磁电弹性体中多条位错与Griffith裂纹（英文）

根据本征方程,研究磁电弹性体中若干平行螺型位错与Griffith裂纹的相互作用.结合Muskhelishvili方法和算子理论,得到磁电弹性体中由位错和裂纹所诱导的应力场、电场和磁场的解析解.数值算例表明:在裂纹的端点及位错点上仍然存在应力的奇异性,离位错点越远处广义力越小,结论与已有的结果相符,证明了结论的正确性.当位错点与裂纹端点距离越近时,裂纹与位错间的应力场越小,并逐渐趋近于零.     

一维六方准晶中螺形位错与楔形裂纹的相互作用

采用保角映射方法和扰动技巧,研究了一维六方准晶中螺形位错和半无限楔形裂纹的相互作用. 讨论了位错的位置和楔形角对作用在位错上的力的影响,得到了应力强度因子和作用在 位错上的力的解析解.此外,还详细地讨论了位错对裂纹的影响.当楔形角参数λ=1/2时, 半无限楔形裂纹退化成半无限尖裂纹,相应的结果 可以作为特殊情况而直接得到.     

单相多铁性材料中静态与动态磁电效应研究新进展

多铁性材料是一类新型多功能材料,其中磁有序与铁电序共存,且序参量之间存在非平庸的相互耦合效应。这使其具有巨大的工业应用前景并蕴含着丰富和有趣的基础物理问题。本文首先简要回顾多铁性材料研究的历史,重点介绍由磁有序引起的新型多铁性材料的实验和理论的新进展。随后,我们系统地概述多铁性材料中演生的一类新的元激发(即电磁振子)的物理特性以及当前对其产生机制的理解。最后,我们总结了多铁性材料研究中尚未解决的技术问题,并展望了多铁性材料的发展趋势。     

磁电弹性材料中含有带四条纳米裂纹的正4n边形纳米孔的反平面断裂问题

基于Gurtin-Murdoch表面理论和保角变换技术,研究了磁电弹性材料中含有带四条纳米裂纹的正4n形纳米孔的反平面断裂问题.得出了考虑表面效应时磁电非渗透边界条件下的应力强度因子、电位移强度子、磁感应强度因子和能量释放率的精确解.数值算例展示了表面效应和孔口尺寸对磁电非渗透边界条件应力强度因子、电位移强度因子、磁感应强度因子和能量释放率的影响.研究发现,考虑表面效应时的应场强度因子、电位移强度因子和磁感应强度因子具有明显的尺寸依赖,并且当孔口尺寸增加到一定程度表面效应的影响开始减小,最终趋于经典弹性理论.     

不同温度下bcc-Fe中螺位错滑移及其与½[11(1)]位错环相互作用行为

采用分子动力学方法模拟研究了不同温度下bcc-Fe中螺位错滑移行为和螺位错与?[11(1)]位错环相互作用机制.结果表明,螺位错在低温2 K剪切应力下主要沿((2)11)面滑移;随温度逐渐升高到823 K,它容易发生交滑移,该交滑移在((1)11)和((2)11)面之间交替进行,因此随温度升高,临界剪切应力逐渐降低.当...     

复合多铁链的磁电耦合行为与外场调控

对含有界面磁电耦合的有限长铁电-铁磁多铁链体系进行了研究,基于矢量离散化思想,构建了描述其磁电性质的微观海森伯模型.利用传递矩阵方法获得了磁化强度、电极化强度、磁电化率等关键热力学量的解析表达式,重点探讨了界面磁电耦合、外场以及单离子各向异性对体系磁电耦合行为的影响和调控.研究结果表明,界面磁电耦合对体系的磁化强度和电极化强度均起促进作用.电场驱动下的电致磁电化率具有更强的磁电关联效应,预示着外电场能够有效地调控体系的磁性行为.而在磁致磁电化率中观察到的低温峰主要源于外磁场的诱导.此外,在高电场作用下体系比热容还呈现出有趣的三峰结构,这种三峰结构是自旋态的热激发以及电偶极矩的电场和温度共同激发导致的.     

多铁异质结构中逆磁电耦合效应的研究进展

电场调控磁性能够有效降低功耗,在未来低功耗多功能器件等方面具有巨大的潜在应用前景.铁磁/铁电多铁异质结构是实现电场调控磁性的有效途径,其中室温、磁电耦合效应大的应变媒介磁电耦合是最为活跃的研究领域之一.本文简要介绍在以Pb(Mg_(1/3)Nb_(2/3))_(0.7)Ti_(0.3)O_3为铁电材料的多铁异质结构中通过应变媒介磁电耦合效应对磁性、磁化翻转及磁性隧道结调控的研究进展.首先讨论了多铁异质结构中电场对磁性的调控;之后介绍了电场调控磁化翻转的研究进展及理论上实现的途径;然后简述了电场对磁性隧道结调控的相关结果;最后在此基础上,对多铁异质结构中电场调控磁性及磁性器件进行了总结和展望.     

体心立方金属钽Ⅱ型裂纹尖端缺陷萌生的多尺度分析

本文采用多尺度准连续介质法(quasi-continuum method, QC)模拟体心立方(body-centered-cubic, bcc)金属钽(Ta)Ⅱ型裂纹尖端位错的形核与发射过程,获得位错发射位置与应力强度因子关系曲线,分析裂纹尖端缺陷萌生过程,研究全位错分解以及扩展位错形成机理. 位错活动在不同阶段表现出不一致的特征,新位错的发射对于位错运动具有促进作用. 研究表明,裂纹扩展初始阶段首先萌生点缺陷,点缺陷随着加载强度增加会萌生新的点缺陷,点缺陷最终运动到边界,导致Ⅱ型断裂破坏. 在全位错发射之前有不全位错的形核与发射表明全位错的分解分步进行,从势能曲线上来看,也就是两个极小值点的形成机理不同. 关键词： 多尺度 准连续介质法 Ⅱ型裂纹 扩展位错     

高温单相多铁性材料与强磁电耦合效应

高温多铁性与强磁电耦合效应是多铁性材料研究领域的两个核心内容。文章首先介绍了已知单相多铁性材料的分类,然后简要综述了一些具有高温多铁性与强磁电耦合效应的代表性材料体系,包括螺旋磁结构六角铁氧体、电荷有序化合物、金属—有机骨架材料等。     

Shielding Effect and Emission Criterion of a Screw Dislocation Near an Interfacial

Shielding effect and emission criterion of a screw dislocation near an interracial crisscross crack are dealt with in this paper. Utilizing the conformal mapping technique, the closed-form solutions are derived for complex potentials and stress fields due to a screw dislocation located near the interracial crisscross crack. The stress intensity factor on the crack tips and the critical stress intensity factor for dislocation emission are also calculated. The influence of the orientation of the dislocation and the morphology of the crisscross crack as well as the material elastic dissimilarity on the shielding effect and the emission criterion is discussed in detail. The results show that positive screw dislocations can reduce the stress intensity factor of the interracial crisscross crack tip （shielding effect）. The shielding effect increases with the increase of the shear modulus of the lower half-plane, but it decreases with the increase of the dislocation azimuth angle and the distance between the dislocation and the crack tip. The critical loads at infinity for dislocation emission increases with the increase of emission angle and the vertical length of the crisscross crack, and the most probable angle for screw dislocation emission is zero. The present solutions contain previous results as special cases.     

A magnetically impermeable and electrically permeable interface crack with a contact zone in a magnetoelectroelastic bimaterial under concentrated magnetoelectromechanical loads on the crack faces

An interface crack with a frictionless contact zone at the right crack-tip between two dissimilar magnetoelectroelastic materials under the action of concentrated magnetoelectromechanical loads on the crack faces is considered. The open part of the crack is assumed to be magnetically impermeable and electrically permeable. The Dirichlet-Riemann boundary value problem is formulated and solved analytically. Stress, magnetic induction and electrical displacement intensity factors as well as energy release rate...     

多航天器并行测试综合显示平台的设计与实现

为解决载人航天器并行测试遥测数据集中判读和关联分析问题,提出一种支持多航天器并行测试的综合显示平台设计方法。对多航天器并行测试方案进行研究,对综合显示平台总体架构进行设计。平台采用插件式程序架构便于功能扩展,采用脚本引擎技术提高平台可配置性,采用MVC设计模式增加页面编辑的可维护性,采用多线程技术和定时器策略实现海量数据的实时显示。平台具备图形页面、列表页面、曲线页面显示功能,可以实现常规数值显示、报警监视及源码、序列显示,同时,支持测试数据本地保存与回放判读。综合显示平台已应用于载人航天器全阶段地面测试和某型号航天器在轨交会对接任务中,应用效果良好。     

The interaction between a screw dislocation and a wedge-shaped crack in one-dimensional hexagonal piezoelectric quasicrystals

Based on the fundamental equations of piezoelasticity of quasicrystal material,we investigated the interaction between a screw dislocation and a wedge-shaped crack in the piezoelectricity of one-dimensional hexagonal quasicrystals.Explicit analytical solutions are obtained for stress and electric displacement intensity factors of the crack,as well as the force on dislocation.The derivation is based on the conformal mapping method and the perturbation technique.The influences of the wedge angle and dislocation location on the image force are also discussed.The results obtained in this paper can be fully reduced to some special cases already available or deriving new ones.     

On the plastic zone size and crack tip opening displacement of a sub-interface crack in an infinite bi-material plate

Elastic–plastic stress analysis has been carried out for the plastic zone size and crack tip opening displacement of a sub-interface crack with small scale yielding. In our study, the shape of plastic zone is assumed as a long, slim strip at both crack tips. In the plastic zone, both normal stress and shear stress exist and are considered due to the bi-material interface. The values of the plastic zone size, normal stress and shear stress are determined by satisfying the conditions where both Modes I and II stress intensity factors vanish and Von Mises yield criterion is met. In the present paper, the sub-interface crack is simulated by continuously distributed dislocations which will result in singular integral equations. Those singular integral equations can be solved by reducing them to a set of linear equations. The values of the plastic zone size and crack tip opening displacement are obtained through an iterative procedure. Finally, the effect of normalized loading, normalized crack depth (distance to the interface) and Dundurs’ parameters on the normalized plastic zone size and the normalized crack tip opening displacement is discussed.