装配体切片图象零件边界轮廓的归并

研究了装配体切片图象零件边界轮廓的归并技术，通过构造材料域，材料域的配准和配准材料域的连续性检查，实现装配体切片图象零件边界轮廓的正确归并。     

装配体ICT图象的内外边界识别研究

用小波变换提取装配体ＩＣＴ图象中的边界轮廓,提出基于简单环识别装配体ＩＣＴ图象的内外边界,该算法可用于装配体的结构形状分析并能正确地建立实体模型。     

面向RP的工业CT切片数据的CLI建模技术研究

主要讨论利用ICT断层图像进行CAD建模并进行快速成形的方法 ,着重研究图像平滑、边缘检测、图像分割、轮廓提取、轮廓特征点采样、轮廓特征点匹配、插值中间轮廓的方法 ,针对摩托车汽缸头复杂零件ICT断层图像进行实验研究 ,取得了较满意的实验结果。     

基于边界矩的机械零件图像轮廓特征提取技术

为实现机械零件的有效分类,针对零件具有比较明显的轮廓特征的特点,提出了基于边界矩的零件图像轮廓特征提取方法.首先采用轮廓提取算法,提取零件二值图像的轮廓,在进行水平倾斜校正后,以零件的质心为中心,将轮廓图像划分为若干个扇形子区域.利用改进的边界矩计算方法,分别计算出各子区域的边界矩,从而得出零件轮廓图像边界矩的分布特性.最后,采用K均值聚类算法对提取的零件轮廓特征进行分类,实验结果证明了该方法的有效性.     

基子CT图像快速成型数据的构建方法

本文针对医学CT图像数据,提出了由CT图像构建快速成型数据的建模方法,确定了CT图像处理方案,即通过对断层图像的预处理、滤波处理、数据提取,生成断层图像轮廓,继而通过对轮廓优化和轮廓冗余数据去除,得到用于三维重建的二维轮廓数据,并在此基础上构造出可直接用于快速原型制造的三维STL数字模型.本文所提出的方法能够大大提高快速医学模型的构建速度.     

基子CT图像快速成型数据的构建方法

本文针对医学CT图像数据，提出了由CT图像构建快速成型数据的建模方法，确定了CT图像处理方案，即通过对断层图像的预处理、滤波处理、数据提取，生成断层图像轮廓，继而通过对轮廓优化和轮廓冗余数据去除，得到用于三维重建的二维轮廓数据，并在此基础上构造出可直接用于快速原型制造的三维STL数字模型。本文所提出的方法能够大大提高快速医学模型的构建速度。     

平面轮廓曲线数据的B样条曲线逼近算法

周期性封闭B样条曲线曲面是医学内植物设计中曲线、曲面造型的主要构造方法.介绍一种断层医学图像目标组织轮廓样条曲线建模方法.首先从断层医学序列图像中提取出目标组织的轮廓曲线,然后采用多边形逼近简化数据点,之后在满足一定控制误差的条件下,用最小二乘法通过B样条曲线逼近轮廓曲线,用尽可能少的数据量表示出各个断层的轮廓曲线,获得医学内植物设计所需的骨组织轮廓曲线模型.     

基于LabVIEW图像识别的物体外观实时分类研究

采用了实时图像与背景图像相减的方法提取物体图像,有效的提高了图像的识别效率。通过对物体轮廓坐标重建的方法提取了边界坐标,及根据型心与边界坐标的欧式距离峰值或峰谷的个数对物体进行了分类识别。通过LabVIEW进行编程,并对圆形、三角形和矩形物体进行实验,结果表明该方法能有效的对物体外观重建,并进行分类。     

基于图像处理的三坐标雕刻机仿真系统的开发

本文对三坐标雕刻机仿真系统进行了研究,通过对图像的读取、图像的处理,用改进的Canny算子对图像边界轮廓的提取,将边界轮廓像素转化为加工刀位点信息。运用Visual C++编程语言与OpenGL图形接口工具,将图像边界在三维环境中再现,最终运用OpenGL仿真技术实现雕刻机的加工仿真,检测加工干涉与动态分析。     

电容层析成像系统三维图像重建及其在两相流体积测量中的应用研究

探讨了电容层析成像系统中利用二维断层图像进行三维表面重建，并由三维图像求取两相流中离散相体积和观察其空间位置的方法。首先对二维断层图像序列进行轮廓抽取和细线化，然后进行轮廓匹配和轮廓插值并进行表面重建；最后利用三维图像求取两相流中离散相体积。初步的仿真结果表明，使用的三维重建算法简单，重建精度高，成像速率快，可以方便地观察离散相空间位置和计算出离散相体积。     

晶界时效析出物对Ni-Cr奥氏体钢高温低周疲劳裂纹萌生和扩展的影响

本文通过裂纹密度,晶界开裂率,裂纹扩展速率和断口金相等的定量测定,讨论了晶界时效析出物对大气和真空中Ni-Cr奥氏体不锈钢高温低周疲劳裂纹的萌生和扩展的影响,并分析了该影响与晶粒大小的关系。时效材的高温低周疲劳裂纹的萌生周次,裂纹扩展速率和扩展方式取决于氧化程度,晶界和晶粒间的相对强度及晶界脆性等因素的综合作用。大气中,晶界时效析出物显著地提高了晶界和晶粒间的相对强度,故有时效析出物的晶界是强的,而真空中有时效析出物的晶界是弱的,因为,晶界时效析出物此起的晶界脆性已成为主要的影响因素。     

CBED and LACBED: characterization of antiphase boundaries

Convergent-beam electron diffraction (CBED) and large-angle convergent-beam electron diffraction (LACBED) techniques are well adapted to the characterization of several types of crystal defects. In fact, dislocations, grain boundaries and stacking faults have already been successfully characterized with these methods. In the present paper, we describe the CBED and LACBED characterization of another type of crystal defect showing a special interest in materials science: antiphase boundaries (APBs). The first part of the paper is devoted to the determination of the effects of antiphase boundaries on CBED and LACBED patterns that could be expected from a theoretical point of view. It indicates that the superlattice excess lines present on these patterns are split into two lines with equal intensity when the incident beam is located on an APB. In the second part, we experimentally test these theoretical predictions on a specimen showing two different known types of antiphase boundaries. In a third part we indicate how these methods could be used to identify unknown APBs in a specimen. Finally, the advantages and disadvantages of both methods for the characterization of antiphase boundaries are discussed.     

First combined electron backscatter diffraction and transmission electron microscopy study of grain boundary structure of deformed quartzite

The structures of boundaries in a deformed and dynamically recovered and recrystallized quartz polycrystal (mylonite) were characterized by transmission electron microscopy, after the misorientation angles across the same grain boundaries had been analysed using electron backscatter diffraction in a scanning electron microscope. In this new approach, a specific sample area is mapped with electron backscatter diffraction, and the mapped area is then attached to a foil, and by the ion beam thinned for transmission electron microscopy analysis. Dislocations in grain boundaries were recognized as periodic and parallel fringes. The fringes associated with dislocations are observed in boundaries with misorientations less than 9°, whereas such fringes cannot be seen in the boundaries with misorientations larger than 17°. Some boundaries with misorientations between 9° and 17° generally have no structures associated with dislocation. One segment of a boundary with a misorientation of 13.5° has structures associated with dislocations. It is likely that the transition from low‐angle to high‐angle boundaries occurs at misorientations ranging from approximately 9° to 14°. Change in the grain boundary structure presumably influences the mobility of the boundaries. In the studied deformed quartz vein, a relative dearth of boundaries between misorientation angles of θ = 2° and θ = 15° has previously been reported, and high‐angle boundaries form cusps where they intersect low‐angle boundaries, suggesting substantial mobility of high‐angle boundaries.     

EBSD characterization of carbide–carbide boundaries in WC–Co composites

A sample of WC‐6wt%Co was investigated for grain boundary character distribution and occurrence of coincidence site lattice (CSL) boundaries on a statistical basis. For this purpose orientation measurements of the grains were carried out using electron back‐scattered diffraction (EBSD). The dominant misorientation relationships were determined by complementary EBSD data representation tools such as orientation maps, misorientation angle distribution histograms and the sectioned three‐dimensional misorientation space. It was found that the grain boundary character distribution of the material is nearly random and the CSL boundaries are not present in statistically significant amounts. It was also found that the amount of binder phase does not play a role in the formation of special boundaries. The paper focuses on the methodology of characterizing grain boundaries in a hexagonal material using EBSD.     

Determination of stability boundaries of shaft movement in a conical bearing with porous surface layer

A method to determine the stability boundaries of shaft movement in a conical slider bearing in the presence of a porous layer on its working surface is developed. Evaluation of the effect of taper angle and porous layer permeability on the dependences determining the stability boundaries of the bearing operation is presented.     

Grain boundary character distributions in Ni-16Cr-9Fe using selected area channeling patterns: Methodology and results

Selected area channeling patterns imaged on an SEM are digitized and displayed on the screen of a Macintosh computer, on which the user selects channeling bands that are measured to determine orientation. Grain boundary misorientations are found using the orientation information for pairs of grains adjacent at grain boundaries, and the boundaries are classified as low angle boundaries (LABs), coincident site lattice boundaries (CSLBs), or general boundaries (GHABs) based on the misorientation information. The technique was implemented to analyze the grain boundary character distributions (GBCDs) in Ni-16Cr-9Fe. The GBCDs of solution annealed material were similar to those expected in an aggregate of randomly oriented polycrystals. However, sequential thermomechanical treatments (5% tensile strain + 945°C:75 min + 2% tensile strain + 890°C:15 h + 3% tensile strain + 890°C:20 h or 9% compressive strain + 890°C:20 h + 9% compressive strain + 890°C:20 h + 3% compressive strain + 890°C:15 h) applied after the solution anneal lowered the proportions of GHABs in the GBCDs from 76–79% to 47–64%. The CSL-enhanced GBCDs of both the tensile-deformed samples and the compression-deformed sample appear to have evolved mainly through impingement of twin and twin-related boundaries during recrystallization; the CSL-enhanced GBCD of a compression-deformed sample appears to have been influenced by grain rotation processes to a greater degree than were the tensile-deformed samples. The CSL boundaries in the CSL-enhanced GBCDs were, in general, closer to the exact CSL misorientations than were those in the near-random GBCDs of the solution annealed material. An analysis of the distribution of misorientation axes did not indicate any correlation between grain misorientation texture and GBCD evolution.     

The Structure Of Interphase Boundaries In Solids

Although, in principle, the structure of solid interphase interfaces should be no different from those of regular grain boundaries in homophase materials, it is shown that special boundaries characterized by a high degree of order occur much more frequently in interphase boundaries than in homophase boundaries. This is mainly caused by the fact that complex phases are usually produced at the end of the processing history of a material. Thus precipitates, eutectics, the products of spinodal decomposition, martensites, surface precipitates, epitaxially-deposited heterojunctions and similar materials all tend to have special boundaries. On the other hand, multiphase materials subject to the same kinds of thermo-mechanical processing as homophase materials, e.g. duplex steels, alloys with grain boundary precipitates, and superplastically deformed materials, possess interphase boundaries closely akin to those of homophase materials. The origins and structural details of the different kinds of boundaries are explored.     

Function-oriented form evaluation of engineering surfaces

Workpieces make contact on their functional boundaries, not on the best fit surfaces. Better quality products can be made by controlling parameters of the production process and evaluating the workpiece based on functional requirements. A new algorithm is proposed in this paper, based on a sound mathematical background, to obtain the functional boundaries that are best represented by enveloping features.     

About the role of boundary conditions on compositional imaging with a scanning electron microscope

We consider the effects of different boundaries on the visibility of a specimen detail providing a compositional contrast in scanning electron microscopy, operating with backscattered electrons or secondary electrons. An object characterized by a gradual variation in composition, an As-doped region in Si, is investigated. The different boundaries in the cross-sectioned specimen correspond to the absence or presence of a poly-Si layer on top of the implanted region, deposited after the annealing treatment. It is shown that the interpretation model used for image formation is of paramount relevance for understanding the experimental results, indicating that the boundaries of the doped region are important in hindering or enhancing its visibility. The relevance of experimental parameters such as electron energy and probe dimension is also reported.     

Low angle boundary migration of shot‐peened pure nickel investigated by electron channeling contrast imaging and electron backscatter diffraction

Study on recrystallization of deformed metal is important for practical industrial applications. Most of studies about recrystallization behavior focused on the migration of the high‐angle grain boundaries, resulting in lack of information of the kinetics of the low angle grain boundary migration. In this study, we focused on the migration of the low angle grain boundaries during recrystallization process. Pure nickel deformed by shot peening which induced plastic deformation at the surface was investigated. The surface of the specimen was prepared by mechanical polishing using diamond slurry and colloidal silica down to 0.02 μm. Sequential heat treatment under a moderate annealing temperature facilitates to observe the migration of low angle grain boundaries. The threshold energy for low angle boundary migration during recrystallization as a function of misorientation angle was evaluated using scanning electron microscopy techniques. A combination of electron channeling contrast imaging and electron backscatter diffraction was used to measure the average dislocation density and a quantitative estimation of the stored energy near the boundary. It was observed that the migration of the low angle grain boundaries during recrystallization was strongly affected by both the stored energy of the deformed matrix and the misorientation angle of the boundary. Through the combination of electron channeling contrast imaging and electron backscatter diffraction, the threshold stored energy for the migration of the low angle grain boundaries was estimated as a function of the boundary misorientation.