3%Si电工钢铸坯中柱状晶的形变、再结晶行为及织构演变规律

利用电子背散射衍射(EBSD)技术和X射线衍射仪(XRD)研究3%(质量分数)Si电工钢铸坯中柱状晶的形变、再结晶行为及织构演变规律。结果表明:柱状晶长轴分别沿轧向、横向和法向放置,具有不同的初始织构。热轧后,表层形成的3种剪切取向中高斯取向较容易形成。中心区,RD样品中的α和γ线轧制取向,TD样品中的强γ线取向,ND样品中的强{100}取向以及各样品中的立方取向,均表现出明显的初始取向依赖性。冷轧后,RD,TD样品中的强{111}〈112〉取向来自热轧板中的高斯取向,ND样品中的强旋转立方取向遗传自初始{100}取向。受初始取向偏差及大晶粒尺寸影响,ND样品中的旋转立方取向晶粒内取向梯度较大。退火后,样品中心大尺寸的{100}取向晶粒是柱状晶初始取向遗传性的表现。     

RSC模型中相互作用系数和标量因子对短纤维取向的影响

为预测注塑成型中短纤维取向分布,提出了在模拟分析中采用RSC纤维取向预测模型对纤维取向分布进行预测的方法。基于RSC取向模型,通过第二顺序张量aij对三维取向分辨率进行描述,采用Orthotropic闭合近似模型对RSC模型进行求解。采用MoldFlow软件对RSC模型的纤维取向分布进行了模拟,分析了相互作用系数Ci及标量因子k对纤维取向的影响。并获得了纤维取向随空间、时间的取向规律——沿宽度方向,两端面的取向要大于中心层,并且端面在开始阶段就能达到很高的纤维取向;沿流动方向,在浇口及充填末端,纤维取向都呈下降趋势,而中间部分则有所增加。     

取向硅钢生产工艺研究进展

结合取向硅钢的传统生产工艺,介绍其生产工艺研究的最新进展,重点介绍了薄板坯连铸连轧生产取向硅钢、异步轧制生产取向硅钢、双取向硅钢生产工艺、磁场退火生产取向硅钢和无抑制剂生产取向硅钢5种取向硅钢生产新工艺。这些新工艺均可在一定程度上提高取向硅钢的性能,有的已进入工业化实践阶段,有的已在实验室取得长足进步。     

薄规格取向硅钢中晶粒取向和尺寸对Goss晶粒异常长大的影响

利用EBSD技术统计了薄规格取向硅钢片中初次再结晶和二次再结晶前期组织中{411}〈148〉、{111}〈112〉、{100}〈025〉取向晶粒尺寸分布,分析了三种不同取向的晶粒对Goss晶粒异常长大的影响。结果表明:初次再结晶组织中不同的取向晶粒对应的平均晶粒尺寸(d)存在差异,{411}〈148〉取向晶粒的平均尺寸最大,其次为{100}〈025〉取向晶粒,{111}〈112〉取向晶粒的平均尺寸最小。Goss取向晶粒异常长大的过程中优先吞噬{111}〈112〉取向晶粒,其次是{411}〈148〉取向晶粒,最后是近{100}〈025〉取向晶粒和近黄铜取向晶粒。{111}〈112〉、{411}〈148〉取向晶粒对Goss取向晶粒异常长大的影响主要体现在二次再结晶的前期。因此,可以推断取向硅钢中最终残留的"岛晶"可能来源于近黄铜取向晶粒或近{100}〈025〉取向晶粒。     

一种镍基单晶高温合金的各向异性研究

研究了一种镍基单晶高温合金[001],[001]和[111]三个晶体取向的组织和性能.结果表明,晶体取向对合金枝晶组织形态和偏析存在显著影响,而合金的弹性模量和持久性能也存在明显的各向异性.在弹性模量方面,[111]取向最大,[011]取向次之,[001]取向最小.对于持久寿命,在871℃/552MPa下,[001]取向的持久寿命最高,[111]取向的延伸率最高;在1010℃/248MPa下,[111]取向的持久寿命最高,[001]取向的延伸率最高;两种实验条件下,[011]取向的持久寿命都最低.     

取向电工钢中Goss晶粒生长的取向环境

将以MnS为主要抑制剂的普通取向电工钢作为实验材料,检测并分析脱碳样品的宏观织构及脱碳和随后加热至925℃时样品的微观织构,统计分析了Goss与周围晶粒的取向差分布。根据取向差原理计算了脱碳样品主要织构组分内各取向晶粒的取向差环境。结果表明,取向电工钢脱碳退火后Goss晶粒与周围晶粒的取向差分布呈现大角度特征,主要取向差分布范围为30°-45°,而非Goss晶粒与周围晶粒的取向差分布则呈现更多小角度特征。二次再结晶后,Goss晶粒与周围晶粒的取向差分布仍然以大角度特征为主。     

聚合物注塑制品的取向研究

概述了聚合物注塑制品的取向机理,取向研究手段.介绍了应用Moldflow软件模拟以及使用偏光显微镜、傅立叶偏光红外光谱仪研究动态注塑制品取向结构的初步结果,指出动态下取向效应明显强于稳态,制品皮层取向产生的光学效应明显强于芯层,红外偏光技术能够较好地对取向态进行定量测试.     

冷轧压下率及初始高斯晶粒取向度对超薄取向硅钢织构演变与磁性能的影响

以不同高斯取向度的取向硅钢成品板为初始原料,采用一次冷轧法制备0.06~0.12mm厚的取向硅钢薄带。利用EBSD取向成像技术研究冷轧压下率以及初始高斯晶粒取向度对超薄取向硅钢织构演变与磁性能的影响。结果表明:随着冷轧压下率增大和厚度减小,退火后再结晶织构增强,当压下率为70%时,再结晶织构中RD∥〈001〉织构最锋锐,磁性能最佳;初始样品高斯取向度越高,制备的薄带样品磁性能越好;因此,生产高性能的取向硅钢薄带应选用初始高斯晶粒取向度较高的成品板。     

聚丙烯腈纤维非晶区的取向结构

基于聚丙烯腈(PAN)纤维中氰基缔合,非晶分子链取向并形成短程有序的堆叠结构,采用X射线衍射仪、声速仪和傅里叶变换红外光谱仪对不同牵伸倍率的PAN纤维的非晶区取向结构进行表征,利用取向因子(fa)和取向相分数(Fa)来研究非晶区取向结构,同时提出了PAN纤维非晶区取向结构演变示意图。结果表明,用X射线衍射法所测得的非晶区取向因子与通过声速法计算所得的非晶区取向因子吻合较好,PAN纤维的非晶区取向因子随牵伸倍率的增加而增大,到某一值时增长趋势逐渐变缓;非晶区取向相分数先降低后增加。     

基于认知取向的虚拟团队整合研究新趋势

对有关虚拟团队的理论研究进行了综合,提出虚拟团队的研究有技术取向、行为取向和认知取向3种主要的研究思路。3种不同的研究取向越来越趋于整合发展。基于认知取向,结合技术取向和认知取向的研究能为虚拟团队研究提供更加良好的整合思路,对于揭示虚拟团队行为过程的本质,解释高绩效团队内在机制具有重要的理论价值和实践意义。     

Prediction of thermoelastic properties in short-fiber composites using image analysis techniques

Methods exist for predicting the effective thermoelastic properties of composite materials, but these methods require a knowledge of the fiber orientation distribution for representative fibers in the composite. Since the orientation of the short fibers used in many composite materials depends strongly on the fabrication conditions, there are infinitely many orientation distributions. Owing to the large numbers of fibers needed to get representative orientation results, digital methods such as the Fourier transform, and semi-manual methods such as a digitizer pad have been introduced for the planar fiber distributions found in many composites. Following a review of these methods, the two-dimensional Hough trandform is introduced as a method uniquely suited for detecting straight line segments such as fibers. In an improved block Hough form, this transform may be used in cases of more dense fiber distributions. A comparison of the results from Hough transform, Fourier transform, and digitizer pad methods have been used for four representative fiber orientations, with sufficient replicates to indicate the relative variance of these three estimators. The results indicate that although the orientation parameters calculated with the Hough transform have a higher variance than those calculated using the Fourier transform, the average predictions for typical thermoelastic properties are quite good, with substantial savings in computation time. Even the outlying value predictions for thermoelastic properties using the Hough transform lie generally within ±5% of the correct values; the Hough transform should thus be considered a viable candidate method for this application. The digitizer pad method gives similar results to Hough transform for 100 fiber samples after cosiderably greater manual effort.     

Gravitaxis screened for physical mechanism using g-modulated cellular orientational behaviour

Advanced methods of recording cellular orientation with respect to the gravity vector are yielding increasingly wellfounded data on gravitaxis. The present study introduces a quantitative method which allows us to predict the precision of orientational behaviour as a function of acceleration assuming static buoyancy as a hypothetical physical principle of gravitaxis. The precision of orientation is expressed by the orientation coefficient as derived from circular statistics. Orientation coefficients calculated from experimental data at various g-values are tested for fit with a sigmoidal orientation coefficient-g-transfer function including a proportionality factor k. Residual orientation values in the low-hypogravity range obey a reciprocal function between k and g. Intersection of this residual-g function with the orientation coefficient-g-relationship gives the minimal acceleration to generate cellular orientation. Those data which clearly diverge from the orientation coefficient-g-curve bear some probability that the observed gravitaxis was guided in part by a physiological mechanism of gravireception and active graviorientation. Data which fit the orientation coefficient-g-curve qualify as being in agreement with a mechanical basis of cellular gravitaxis. Examples from the literature are presented and discussed in the light of our scheme of gravitaxis screening.     

Contrast enhancement via texture region based histogram equalization

Abstract

This paper presents two novel contrast enhancement approaches using texture regions-based histogram equalization (HE). In HE-based contrast enhancement methods, the enhanced image often contains undesirable artefacts because an excessive number of pixels in the non-textured areas heavily bias the histogram. The novel idea presented in this paper is to suppress the impact of pixels in non-textured areas and to exploit texture features for the computation of histogram in the process of HE. The first algorithm named as Dominant Orientation-based Texture Histogram Equalization (DOTHE), constructs the histogram of the image using only those image patches having dominant orientation. DOTHE categories image patches into smooth, dominant or non-dominant orientation patches by using the image variance and singular value decomposition algorithm and utilizes only dominant orientation patches in the process of HE. The second method termed as Edge-based Texture Histogram Equalization, calculates significant edges in the image and constructs the histogram using the grey levels present in the neighbourhood of edges. The cumulative density function of the histogram formed from texture features is mapped on the entire dynamic range of the input image to produce the contrast-enhanced image. Subjective as well as objective performance assessment of proposed methods is conducted and compared with other existing HE methods. The performance assessment in terms of visual quality, contrast improvement index, entropy and measure of enhancement reveals that the proposed methods outperform the existing HE methods.     

单晶高温合金晶体取向的研究进展

单晶高温合金晶体取向与轴向的偏离已成为单晶叶片的一个重要缺陷.简述了单晶生长过程中在不同界面形态下择优取向的转变规律,以及取向对枝晶形貌和尺度的作用;分析了不同取向晶粒的竞争机制,并展望了晶体取向今后研究发展方向;指出了温度梯度、界面形状、熔体等是影响单晶高温合金晶体择优取向的重要因素.     

Integrated method for tool path generation in five-axis sculptured surface machining

Five-axis machining allows continuous adjustment of cutter orientation along a tool pass. Unfortunately, the flexibility has not been fully exploited due to the separate consideration of tool path generation and cutter orientation in current machining methods. This paper presents an integrated method (IM) for tool path generation, which is tightly integrated with the orientation strategy, to minimise tool path length under the constraint of smooth cutter orientation. Distinctively, cutter orientation along a tool pass is optimised by balancing considerations of maximum material removal and smoothness of cutter movement. Further, the intervals between successive tool passes are maximised according to the optimised orientation. In the paper, the IM is combined with the quadric method, a recently developed cutter orientation strategy, for iso-parametric machining with a flat-end cutter. However, the method could be applied to other orientation strategies with different machining mechanisms and cutter types. Simulated examples illustrate that the IM is more efficient in machining than established methods.     

Template‐Free,Surfactant‐Mediated Orientation of Self‐Assembled Supercrystals of Metal–Organic Framework Particles

Mesoscale self‐assembly of particles into supercrystals is important for the design of functional materials such as photonic and plasmonic crystals. However, while much progress has been made in self‐assembling supercrystals adopting diverse lattices and using different types of particles, controlling their growth orientation on surfaces has received limited success. Most of the latter orientation control has been achieved via templating methods in which lithographic processes are used to form a patterned surface that acts as a template for particle assembly. Herein, a template‐free method to self‐assemble (111)‐, (100)‐, and (110)‐oriented face‐centered cubic supercrystals of the metal–organic framework ZIF‐8 particles by adjusting the amount of surfactant (cetyltrimethylammonium bromide) used is described. It is shown that these supercrystals behave as photonic crystals whose properties depend on their growth orientation. This control on the orientation of the supercrystals dictates the orientation of the composing porous particles that might ultimately facilitate pore orientation on surfaces for designing membranes and sensors.     

产品设计定位观

强调了设计定位在产品设计中的重要性,通过分析在商品流通过程中,产品、商品及消费品之间的概念转换,对设计定位在不同阶段的合理考虑进行了阐述,并提出了具体的设计定位方法。     

Magnetic-field-assisted formation of alignment polymer coatings in liquid crystal cells

We describe a new method for obtaining liquid crystal (LC) layers with planar orientation in plane-parallel cells, which is based on the technology of LC-polymer interface formation in solution under the action of an applied magnetic field. The azimuthal anchoring energy of LC at the polymer surface has been determined by measuring the angle of orientation of the nematic LC director on the substrate surface as a function of the magnetic field. The LC orientation provided by the proposed method is stable, and the anisotropy of LC anchoring is comparable with that achieved using well-known methods of alignment polymer film preparation by rubbing.     

Impact of fibre orientation on tensile,bending and shear behaviors of a steel fibre reinforced concrete

Fibre orientation and density are known to have a significant influence on steel fibre reinforced concretes (SFRC) mechanical properties. In practice, parameters such as fresh state properties, restriction to concrete flowability and placing methods are likely to induce different fibre orientations in characterisation specimens and structural components. This difference in fibre orientation can impact the mechanical behavior of the structural component and therefore provide an unsafe design if not considered. This project consisted to produce a large SFRC slab, extract specimens with different fibre orientations, and submit specimens to tensile, bending and shear tests to evaluate the impact of fibre orientation and density on mechanical and post-peak strengths. Test results have shown that tensile and bending behaviors are mainly influenced by the fibre orientation, while the shear behavior is mainly impacted by fibre density. Test results were processed to allow comparison between tensile and bending tests. Linear correlations between tensile residual stresses and fibre orientation where found, linear or power type correlations according to bending residual stresses, as well as linear correlations between shear stresses and fibre density.     

Crystal orientation of non-magnetic materials by imposition of a high magnetic field

From the view point of learning from the nature, the controlling of crystal orientation is accounted to be a major subject for materials processing. This paper reviews the researches on the crystal orientation by use of a high magnetic fieldand belongs to the category of researches for mimicking structures, namely the crystal orientation, which nature or livingbodies are forming. Regarding to the crystal orientation, several methods such as unidirectional solidification and epitaxial growth and so on have been developed hitherto. On the other hand the magnetization force that is familiar with the force to attract iron to a magnet, has been recognized to be effective even in non-magnetic materials when those are placed under a high magnetic field, which has become rather conveniently available by developing superconducting technologies in these days. In this paper, main results obtained when the imposition of a high magnetic field was accompanied to several materials processing such as electrodeposition, vaperdeposition, solidification, baking, slip-casting and precipitation, arereviewed from the view point of crystal orientation of non-magnetic materials.