基于Geomagic的曲面重构方法研究

阐述了散乱数据点的曲面重构的方法,重构出不同结构物体的三角网表面模型.首先根据扫描点云的分布特点、疏密程度等实际情况,分析影响重构曲面的关键因素,然后按照正向设计的思想,分析零件的外形,发挥不同曲面拟合的优势.结合典型逆向软件Geomagic对曲面造型方式的特点及应用进行研究与分析.进而规划两个零件的重构路径,达到了良好效果,为复杂零件的重构提供了借鉴意义.     

复杂曲面边界线自动提取技术研究

复杂曲面零件的几何模型重构是逆向工程的研究重点之一,由零件表面的数字化数据提取边界线是构造几何模型的重要步骤。针对由CMM获取的三维数据“点云”,提出了经纬线扫描算法自动提取单值曲面边界线,提出了基于局部增量网格扩张的三维散乱数据三角剖分算法,实现了任意非封闭曲面边界线的自动提取。实践证明,通过该算法得到的复杂曲面的边界线能够满足模型重建的工程需求。     

基于Solid Works的法兰三维参数化设计

在产品设计中,存在着一些尺寸不同但结构形状相同或相似的零件,导致了大量的重复性劳动.为了提高零件设计和零件造型的效率,文章以法兰为例,论述了在Solid Works环境下,利用Visual Basic 6.0实现零件三维参数化设计的方法.利用该方法能实现零件国际数据的自动查询,三维造型的自动实现.文章阐述了程序实现的总体思路和结构,论述了数据库的访问技术、应用程序的加载方法以及零件三维参数化设计等若干关键技术,给出了设计实例.     

基于逆向工程的覆盖件三维建模技术的研究

逆向工程作为产品制造的一种手段,可以将符合要求的汽车覆盖件零件进行测量并反求出零件的三维模型。本文采用逆向工程技术,通过3DD-300型三维激光非接触扫描仪得到覆盖件的点云图,在PRO／E中完成了点数据的处理、曲线和曲面的构建、修边等工作,利用小平面特性最终生成了覆盖件的三维模型。     

复杂曲面的零件逆向建模及其仿真分析

由于复杂零件建模周期长,而且不利于二次创新,应用逆向工程对其进行建模能很好的解决此问题,并对所得模型进行仿真分析得到满足要求的模型。文章以控制臂的三维模型的建立及性能研究为例,首先,使用三维激光扫描仪获得控制臂的扫描数据;然后应用逆向软件Geomagic Studio对所得数据进行点云处理,然后建立三维模型;最后应用有限元分析软件ANSYS Workbench对得到的模型进行仿真分析,若仿真分析后结果不满足要求,则对模型进行重构,直至满足要求为止。通过该方法可以快速获得满足性能要求的控制臂模型,并且有利于复杂曲面零件进行二次创新。     

面向层析测量的特征模型反求系统

针对断层测量反求,邮基于物体基本结构和特征的轮廓分割算法。新算法具有分割效率高、分割准确的优点。断层测量截面方位的不同使得同一特征的截面形状具有多样性，给特征参数的识别造成很大困难。为了解决这一问题，提出对分割后的特征结构轮廓集进行“二次虚拟层切”的方法，使特定特征类型的截面形状固定下来，大大降低了特征参数识别的难度。系统可以获得反求零件的参数化CAD模型，使得对重构模型的方便修改成为现实。     

重构模型精度的评定和产品改进

以叶片CT 扫描后的数据点云为研究对象,对其进行数据预处理、曲线拟合以及重构模型.针对重构模型采用了两种方式评定重构模型质量,第一种方式是以叶片重构模型与其CAD模型的均方误差、平均误差以及最大误差来评定总体重构精度.另一种方式就是以重构模型上的截面曲线与CAD模型上的对应理论曲线的均方误差、平均误差、最大误差、截面曲线周长和截面面积来评定重构模型局部重构质量.此外,在重构模型的过程中,对拟合的曲线进行等比例缩放,从而改进产品模型,得到一系列形状相同,尺寸不同的产品族.     

基于逆向工程的虚拟设计研究

基于逆向工程的再设计是现代设计的一种有效新方法，虚拟设计有必要采用反求技术来充实它的设计方法和专家库系统。文章首先对机电系统进行基于逆向工程的系统设计分析，找到系统反求虚拟设计的集成化模型结构，并建立了系统反求虚拟设计的各个模型。然后，对系统中零件的实体反求虚拟设计的体系结构、零件三维模型重构的关键技术进行了研究，从而完成基于逆向工程的虚拟设计。     

基于BP神经网络的新零件材料消耗定额预测方法研究

为精确地预测熔模铸造中新零件材料消耗定额，采用了BP神经网络的方法进行建模。在分析影响各工序零件材料消耗主要因素的基础上，确定了BP神经网络模型的特征参数，并根据实际情况确定了输入层和隐含层的神经元个数，从而确定了模型的结构。用试验数据对模型结构进行训练，最终建立了一个用于新零件材料消耗定额预测的BP神经网络模型。     

基于快速成型的病态膝关节建模技术

针对医学领域中人工关节制造的多样性、复杂性的特点,提出了一种基于CAD技术和快速成型技术的膝关节三维建模方法。以膝关节CT图片为数据源,通过灰度分割法调整阈值,提取骨骼层片边缘轮廓,导入CAD软件,经过曲线重构、曲面重构实现三维模型重构,输出STL文件,采用快速成型技术制造出膝关节原型。结果表明：该技术可以实现个体化人体器官快速成型三维模型的准确构建。     

Epitaxial growth and mechanical properties of (001) ZrN/W nanolaminates

Epitaxial growth of ZrN/W multilayers with bilayer periods Λ ranging from 2.5 to 50 nm has been achieved at 300 °C on MgO (001) substrates by means of dual ion beam sputtering, which is a novelty compared to polycrystalline growth reported so far in this system. X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM) experiments reveal the following epitaxial relationship [110] (001) W // [100] (001) ZrN // [100] (001) MgO. Nanoindentation tests indicate a hardness increase proportional to Λ^− 0.54, with maximum of 25.8 GPa at Λ = 2.5 nm. However, there is no hardness enhancement relative to rule-of-mixtures value, which could be ascribed to delamination at the W on ZrN interfaces, as observed by TEM and related to large compressive stress, as determined by XRD. Another explanation could be related to the small difference in shear modulus between the two materials.     

Platinum colloid catalyzed etchingless gold electroless plating with strong adhesion to polymers

Echingless electroless plating (ELP) process that can produce gold thin film with strong adhesion to various polymer films has been developed. We have found that platinum (Pt) colloidal nanoparticles have excellent catalytic activity for ELP. The Pt colloidal nanoparticles can be immobilized via electrostatic interactions on a substrate simply by dipping it into a Pt colloid. Owing to the excellent catalytic property of the Pt nanoparticles, continuous gold thin films can be produced at room temperature using a simple cyanide-free gold electroless plating solution composed of chloroauric acid and hydrogen peroxide. The process requires no surface modifications for the immobilization of the catalyst, and by simple post-annealing the adhesion of the plated films to various polymer films can be improved by three orders of magnitude in comparison to that of “as-deposited” film. The process developed in this work is expected to be an environment-friendly thin metal film deposition process without the use of toxic and hazardous substances.     

Surface analyses and biocompatibility study of 500 °C oxidized Ni50Ti50 and Ni40Ti50Cu10 shape memory alloys

Ni₅₀Ti₅₀ and Ni₄₀Ti₅₀Cu₁₀ shape memory alloys (SMAs) are oxidized at 500 °C. Considering the surface roughness, the thicknesses of oxide layer and Ni-free layer, the surface Ni concentration, the proper oxidation times for oxidized specimens are found to be 60 min for Ni₅₀Ti₅₀ and 30 min for Ni₄₀Ti₅₀Cu₁₀. Experimental results reveal that the oxidation is diffusion-controlled with its oxide layer containing titanium oxide and that the surface Ni concentration is much lower than the nominal composition. When Ni₅₀Ti₅₀ and Ni₄₀Ti₅₀Cu₁₀ SMAs are oxidized at these times, the latter has better corrosion resistance than the former in Hanks' solution at 27 °C. However, the results of cytotoxicity and cell proliferation assays indicate that the biocompatibility of unoxidized Ni₄₀Ti₅₀Cu₁₀ is worse than that of unoxidized Ni₅₀Ti₅₀, but that of oxidized Ni₄₀Ti₅₀Cu₁₀ ranks as good as that of oxidized Ni₅₀Ti₅₀.     

Study on the stability of plasma-polymerized fluorocarbon ultra-thin coatings on stainless steel in water

Metallic stents are thin wire mesh tubes implanted in partially blocked arteries to prevent the obstruction of blood flow and to act as internal scaffolding. Mainly made of 316L stainless steel, they are prone to localized corrosion attack in long-term applications which in turn causes the release of potentially toxic ions such as chromium and nickel. To improve the long-term performance and safety of stainless steel stents, a multi-step process was previously developed in our laboratory to isolate the stainless steel surface from the body fluid by coating the metal with an ultra-thin cohesive and adherent plasma-polymerized fluoropolymer coating (Teflon-like ultra-thin coating). In this context, the aim of the present study was to evaluate the stability of the Teflon-like ultra-thin coating in deionised (D.I.) water using static immersion tests. Deionised water was selected as ageing medium mainly because it did not contain any compounds that might deposit onto the surface and interfere with further surface analyses. After periods of immersion in D.I. water ranging from 1 to 4 weeks, chemical and morphological characterization of the coating, both in its bulk and surface, was carried out by atomic force microscopy (AFM), ellipsometry, Fourier-transform infrared spectroscopy (FTIR), contact angle measurements (CA) and X-ray photoelectron spectroscopy (XPS). Results have shown that upon ageing, there is a decrease in the fluorine concentration and an oxidation of the coating. The degradation of the coating could probably result from the water, which penetrates the coating and induces changes in the chemical composition and microstructure.     

In situ composite coating of titania-hydroxyapatite on commercially pure titanium by microwave processing

Microwave (MW) processing has been studied as an alternative method of hydroxyapatite (HA) based composite coatings on commercially pure titanium (CPTi) to enhance the bioactivity for orthopaedic and dental implant applications. The coating was formed by processing CPTi metal packed in HA and at 800 W microwave power for 22 min. The composition of the coating was found to be TiO₂ (rutile) as major phase along with HA as minor phase. The MW absorption of non-stoichiometric TiO₂ layer, which was grown during the initial hybrid heating, resulted in sintering of apatite particles interfacing them. The non-stoichiometric nature of TiO₂ was evident from the observed mid-gap bands in ultraviolet-visible diffusive reflectance (UV-VIS-DR) spectrum. The lamellar α structure of the substrate suggests that the processing temperature was above β transus of CPTi (1155 K). The oxygen stabilized α phase whose thickness increased with microwave processing time, was likely to be the reason for the increase in Young's Modulus and hardness of the substrate. The coating induced apatite precipitation in bioactivity test. The osteoblast cell adhesion test demonstrated cell spreading which is considered favourable for cell proliferation and differentiation. Thus, in situ composite coating of titania and HA on CPTi was obtained by a simple one-step process.     

Elaboration of thin films based on p-tert-butyl-calix [8] arene. Application to the chemical sensors type EIS and ISFET

In this paper we report some results about recognition reagents in an EIS (electrolyte—insulator—semiconductor) and ISFET (ion-sensitive field-effect transistor) type sensors, elaborated with a p-tert-butyl-calix [8] arene molecule. This calixarene was deposited by sublimation onto the surface insulator of the samples. Reflexion—adsorption infrared spectroscopy and X-ray diffraction were performed to characterize the chemical properties and the morphology of the layers. Electrochemical measurements were made to study the sensitivity and the selectivity of this sensitive membrane towards earth alkaline cations and the transition metals. A linear sensitivity was obtained only for the Ca²⁺. These devices exhibit a high chemical stability in liquid media and consequently can be used as sensors.     

Neurofuzzy approach to process parameter selection for friction surfacing applications

Friction surfacing is an advanced manufacturing process, which has been successfully developed and commercialised over the past decade. The process is used for corrosion and wear resistant coatings and for reclamation of worn engineering components. At present, the selection of process parameters for new coating materials or substrate geometries experimentally requires lengthy development work. The major requirement is for the flexibility to enable rapid changes of process parameters in order to develop new applications, with variations of materials and geometries in a cost effective and reliable manner. Further improvement requires development of appropriate mathematical models of the process, which will facilitate the introduction of optimisation techniques for efficient experimental work as well as the introduction of real time feedback adaptive control. This paper considers the use of combined artificial intelligence and modelling techniques. It includes a new frame of a Neurofuzzy-model based Decision Support System — FricExpert, which is aimed at speeding up the parameter selection process and to assist in obtaining values for cost effective development. Derived models can then be readily used for optimisation techniques, discussed in our earlier work.     

Nanoindentation response of PEEK modified by mesh-assisted plasma immersion ion implantation

Polyetheretherketone (PEEK) surfaces have been treated by mesh-assisted plasma immersion ion implantation, significantly altering the viscoelastic properties of the near-surface modified region. The plasticity index derived from nanoindentation load-displacement data indicates that the treated surfaces exhibit greater elastic recovery and reduced plastic deformation compared to unmodified PEEK. Scanning probe microscopy (SPM) images of the surface before and after indentation also show evidence of increased elastic recovery.     

Effect of overall composition on thermally induced solid-state transformations in thick EB PVD Al/Ni multilayers

Multilayered Ni/Al samples 20–70 μm thick of different average stoichiometries were prepared by electron-beam physical vapour deposition technique. The periodicity in the multilayers varied between 0.2 μm and 0.8 μm. The course of the solid-state transformations initiated by heating the samples at a constant rate has been studied. Intermetallic Al₃Ni was found to be the first phase to form upon heating of all samples studied. Further reactions were dependent on the average composition of the sample so that Al–Ni compounds increasingly richer in Ni formed as the nickel content increased. In general, the phases Al₃Ni, Al₃Ni₂, AlNi, and AlNi₃ have been observed upon heating the samples to 600 °C. The phases were more likely to form in succession rather than to grow simultaneously.     

Atmospheric pressure chemical vapour deposition and characterisation of crystalline InTaO4, InNbO4 and InVO4 coatings

The possibilities to grow crystalline complex InTaO₄, InNbO₄ and InVO₄ coatings as well as single oxide layers In₂O₃, Ta₂O₅, Nb₂O₅, and VO_x were investigated using aerosol assisted atmospheric pressure chemical vapour deposition technique. Indium(III) and niobium(IV) tetramethylheptanedionates, tantalum(V) tetraethoxyacethylacetonate and vanadium(III) acethylacetonate were used as precursors, monoglyme and toluene as solvents. The influence of deposition conditions and solution composition on elemental and phase compositions of layers was studied. Indium tantalate layers containing pure monoclinic InTaO₄ phase were obtained ex-situ, i.e., after high-temperature (800 °C) annealing of layers grown at lower temperature (500 °C). Films containing pure orthorhombic indium vanadate or monoclinic indium niobate phase may be prepared using both in-situ (600 °C) or ex-situ (deposition at 400 °C, annealing at 800 °C) approaches. Under optimised deposition conditions and solution compositions, Ni-doped InVO₄ and InTaO₄ films were also deposited and their photocatalytic activity was tested.