Journal of Applied Physics
Based on the developed multiple-scattering theory [C.-W. Nan and F. S. Jin, Phys. Rev. B 48, 8578 (1993)], an effective-medium theory (EMT) is proposed to treat coupled electromechanical behavior in composite media. The explicit relations for determining effective behavior of piezoelectric composites are derived. To illustrate the technique, numerical results of piezoelectric ceramic/epoxy composites for various particle shapes are presented over the whole range of concentrations. The EMT estimates are shown to be in good agreement with available experimental results. Porous piezoelectric ceramics are also discussed. The EMT predicts a similar critical behavior for heterogeneous piezoelectric materials to recent experiments.
关键词:
electromechanical properties;ceramics
Acta Materialia
In a first report [Jin ZH.. Gumbsch P, Ma E, Albe K, Lu K, Hahn H, et al. Scripta Mater 2006;54:1163], interactions between screw dislocation and coherent twin boundary (CTB) were studied via molecular dynamics simulations for three face-centered cubic (fcc) metals, Cu, Ni and Al. To complement those preliminary results, purely stress-driven interactions between 60 degrees non-screw lattice dislocation and CTB are considered in this paper. Depending on the material and the applied strain, slip has been observed to interact with the boundary in different ways. If a 60 degrees dislocation is forced by an external stress into a CTB, it dissociates into different partial dislocations gliding into the twin as well as along the twin boundary. A sessile dislocation lock may be generated at the CTB if the transited slip is incomplete. The details of the interaction are controlled by the material-dependent energy barriers for the formation of Shockley partial dislocations from the site where the lattice dislocation impinges upon the boundary. (c) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
关键词:
dislocation;slip;twinning;twin grain boundary;molecular dynamics;molecular-dynamics simulation;grain-boundaries;nanocrystalline;materials;cross-slip;rate sensitivity;deformation;copper;strength;aluminum;fcc
周镇
,
艾育华
,
孔文俊
工程热物理学报
本文利用双腔泄压式定压燃烧弹,研究了高压下典型IGCC合成气的层流火焰传播特性,得到了不同压力(0.1～1 MPa)和不同当量比下(0.6～3.0)合成气的层流火焰传播速度和Markstein长度.实验结果表明,层流火焰传播速度随当量比先增加后减少,随压力的增加而减小.Davis和Sun机理能较好地预测高压下合成气层流火焰的传播速度.Markstein长度随当量比的增加而增加,随压力的增加而减小.
关键词:
合成气
,
球形火焰
,
层流火焰传播速度
,
Markstein长度
程杰锋
,
唐广波
,
刘正东
钢铁研究学报
选取了现有典型的C-Mn钢相变过程的物理冶金模型,包括5组孕育期模型、7组相变动力学方程模型、5组相变后铁素体晶粒尺寸模型.利用自行开发的组织性能预报系统软件模拟计算了在3组实际冷却工艺条件下各模型的奥氏体转变过程,并对各模型进行了评价.结果表明,对于所设定的成分和工艺条件,适用性较好的孕育期模型是Kwon所提出的模型;适用性较好的动力学方程模型是Liu、Donnay和Sun所提出的模型;适用性较好的铁索体晶粒尺寸模型是Hodgson所提出的模型.
关键词:
孕育期
,
相变
,
适用性分析
朱亮
,
肖毅
复合材料学报
为满足在工程应用中对建立拉压性能不同纤维增强复合材料的非线性本构理论的需要,考虑静水压影响的Drucker-Prager屈服准则与各向异性的Hill屈服准则相结合,提出了广义Hill屈服准则,并推广到Sun-Chen的单参数塑性模型中,建立了考虑拉压异性复合材料的非线性统一本构方程.实验验证结果表明,运用本文中所建立的本构模型能够很好地描述碳纤维/环氧(IM600/Q133)复合材料在偏轴拉伸和压缩载荷作用下的非线性响应.
关键词:
单向复合材料
,
非线性响应
,
不同屈服强度
,
本构方程
,
偏轴拉伸-压缩载荷
郝寅雷
无机材料学报
doi:10.3321/j.issn:1000-324X.2003.02.007
建立在均匀、无应力状态基础上的玻璃性质计算模型,在用于离子交换法制备的GRIN光学元件的折射率变化值(ΔN)计算时与实验结果有一定的偏差.本文对HSD(Higgins,Sun和Davis)模型和干福熹模型进行了比较,结果表明,干福熹模型用于低应力光学元件的计算时计算结果与实验值偏差较小,但对高应力GRIN光学元件的ΔN计算偏差很大;HSD模型在计算过程中分别考虑了玻璃组分的极化率因素和体积因素对其折射率的影响,在用于高应力GRIN光学元件ΔN计算时具有更强的适用性.
关键词:
梯度折射率
,
离子交换
,
玻璃
,
模型
