过程装备产品设计系统的研究与开发

以面向对象思想和参数化造型技术为指导,通过C 程序语言、MS SQL Server2000数据库和UG NX二次开发工具,构建过程装备产品设计系统,最终实现过程装备部件的结构设计计算、三维几何模型快速造型以及模型管理等功能.详细介绍了该系统的体系结构及实现方法,着重阐述设计计算、几何造型、数据管理等功能的实现方法,并以换热器为实例加以说明,其他过程装备可在系统框架下方便地扩充.     

包装容器虚拟造型三维表现与设计效果案例精解

本文对包装容器造型的计算机辅助设计虚拟三维设计表现作深入探讨.并详细论述了其具体的创作内容和意义.通过包装容器造型设计案例详细解析多个设计软件的交互结合使用,以及相关软件命令与参数的具体控制和调整方法,制作出预想的包装容器虚拟造型三维表现效果,明晰了创建虚拟模型的过程与创作方法.     

基于结构特征的海量三维模型管理方法

虚拟现实和3D可视化技术的发展带来三维模型的海量增长,传统方法采用关键字匹配方式检索和管理海量模型数据,不能满足语义级别的模型检索和管理要求.提出一种基于结构特征的海量三维模型管理方法.使用该方法的思路框架,分析海量模型实例,通过聚类与分类的方法进行概念发现,构建管理特定领域的本体库,基于本体库设计并实现基于结构特征的三维模型管理系统,最后对系统进行应用和验证.结果表明该方法很好地解决了传统三维模型管理从单一维度管理模型的低效、冗余和难以重用,实现了三维模型的多维度高效检索和管理.     

基于球面调和映射的三维产品形态融合方法研究

三维产品形态的创新设计在产品造型设计中具有重要的地位,是提高产品竞争力的重要手段。基于球面调和映射,提出一种新算法,在两个产品之间实现形态的变形,进而产生多种产品形态。首先对两个三维产品形态划分三角网格;然后将网格化的产品形态嵌入到一单位球面上,生成嵌入体模型,该嵌入体与其三维产品形态有着相同的拓扑结构;最后将这两个嵌入体融合,在两个形态之间建立一种对应关系,通过线性插值生成一系列的中间形态。以两个不同形态的鼠标基体模型为例进行实验研究,结果表明该算法对于产品形态的融合具有很好的适用性。在计算机辅助产品形态造型设计中将具有良好的应用前景。     

基于参数化理论模型的车架造型设计

探索基于非线性科学的参数化理论模型对车架造型设计的启发与应用,通过对现代数学的分析,论文提出了拓扑、突变、分形三种产品造型参数化理论模型,并将其应用到车架造型设计中,设计出新颖外观形态的车架。参数化设计是一种紧密结合时代的设计思想和技术工具,能够帮助设计师创造和处理复杂的产品形态,给车架造型设计带来了巨大的自由空间,同时依靠参数化设计数学逻辑的操作形式,构建车架参数化模型。     

三维分形图案自动生成方法及其应用研究

为了实现分形图案计算机辅助三维化设计,以生成产品造型触感装饰效果,提出一种集成Visual C++、AutoCAD、Pro/E的三维分形图案自动生成方法。应用ObjectARX3.0开发了分形图案参数化自动生成软件,可简易获取各种分形图的.dwg(或.dxf)格式文件;在Pro/E软件中调入.dwg(或.dxf),通过其拉伸、扫描和映射等操作实现分形图的三维化设计。实例表明该方法可应用于产品造型设计中立体纹案的设计与实现。     

基于认知耦合的加湿器设计

目的 把认知耦合理论引入产品形态设计中,得出符合认知耦合理论的设计方案.方法 首先通过语义差分法获得产品目标感知意象,依据意象词汇寻找仿生对象,能够同时实现形态耦合和语义耦合;其次通过拓扑结构的方法对生物原型进行特征层次分析,筛选最强特征,通过拓扑权值和拓扑相似度得出最佳仿生形态,最后运用模糊综合评价法评定耦合度,确定设计方案.结果 仿生鹦鹉鱼形态,分析特征拓扑图与结构特征,通过模糊综合评价法确定加湿器设计方案,实现了造型认知耦合与语义认知耦合.结论 将认知耦合理论与仿生设计结合作为此次设计理论总结的设计方法运用到产品设计中,可以满足产品造型需要,也可以满足加湿器的语义需求,这是一种新的设计思路,具有研究意义.     

基于顶层基本骨架TBS模型的变型设计

介绍了基于顶层基本骨架TBS模型的变型设计相关概念.以三维参数化特征造型软件Pro/ENGINEER为平台,并结合手机设计实例,论述了在自顶向下的数字化装配模式过程中,以TBS模型为核心的实现变型设计的方法和步骤.经实践证明此方法可以缩短产品开发周期,保证高效、高质量、低成本地开发新产品.     

基于SolidWorks的包装容器结构参数化设计

主要介绍了采用SolidWorks二次开发实现塑料固体药瓶的结构三维参数化设计,实现了直接输入参数后自动实现产品的精确造型,使包装工程技术人员对SolidWorks在包装结构参数化设计的应用有一个明确的了解,对其他材料的包装容器结构的三维参数化设计有着很大的借鉴作用.     

玉米根系几何造型研究

通过对玉米根系形态建成过程根系的结构、生长及分布特点和规律观测研究,构建了描述玉米根系形态变化的数学模型。结合粒子系统和计算机图形学技术,在计算机上实现了玉米根系生长的三维显示。其结果和实际的玉米根系的生长发育过程基本一致,为农学研究者提供了一个可视化的根系模型。本模型结构简单、可交互、真实感强,可以较好地虚拟玉米根系的生长过程。     

孔隙形状及孔隙率对多孔材料弹性性能的影响

利用通用单胞法(GMC)计算了不同孔隙形状及孔隙率对多孔材料等效弹性参数的影响,计算中分别采用二维方形、圆形孔隙模型和三维立方体、球形孔隙模型模拟多孔材料。不同孔隙率下等效弹性参数的计算结果表明: 不同孔隙形状下,多孔材料等效弹性参数随孔隙率增大的退化程度不同;通过对比二维简化模型与三维模型的差异,发现二维简化模型对多孔材料等效弹性参数的估算值偏低。进一步将GMC计算结果和已有文献实验结果进行比较,发现两者具有较高的吻合度。最后将GMC模型与有限元、经验模型进行对比,得出GMC模型的局限性。综合计算结果,GMC具有一定的计算精度,可应用于工程实际分析中。     

Theoretical and experimental investigation of steady-state voltammetry for quasi-reversible heterogeneous electron transfer on a mercury oblate spheroidal microelectrode.

A mercury microelectrode formed by electroreduction of mercury on an inlaid gold microdisk is experimentally shown to be well modeled by oblate spheroidal geometry when the ratio of the semiminor axis to the semimajor axis of the protruding drop is less than 1. The validity of the geometry is established by comparison of the experimentally determined coefficient in the steady-state diffusion current equation with the theoretical value for oblate spheroidal geometry. Spherical cap geometry is also shown to be an equally valid geometric model; however, theoretical treatment for this system is more difficult. The theory of a quasi-reversible electrode process is developed and applied to the determination of the electrode parameters of the RuIII(NH3)6/RuII(NH3)6 electrode reaction on a mercury oblate spheroidal microelectrode. Results agree well with others found in the literature for the same process on a mercury electrode.     

Characterization of microstructure in stitched unidirectional composite laminates

The internal geometry of stitched uniaxial multiply carbon-fiber preforms is investigated experimentally. The microstructure is parameterized by such four introduced parameters as distortion length, distortion width, minor axis and major axis. The quantificational measurements are performed for these parameters under different stitch densities and different stitch threads. A theoretical model, called fiber distortion model, is developed to describe the spatial distribution of in-plane fiber misalignment angle and inhomogeneous fiber volume fraction induced by stitching.     

MODAL APPROACH FOR PROCESSING ONE- AND THREE-POINT BEND TEST DATA FOR DSIF–TIME DIAGRAM DETERMINATION. PART II—CALCULATIONS AND RESULTS

In Part I of this paper, using the modal superposition method, equations for dynamic SIF calculations are derived for an arbitrary linear model of an impact bend specimen. In this paper (Part II), modal parameters and other data which are necessary for the DSIF determination have been calculated for three types of specimen model: the Euler–Bernoulli beam model, and two- (2D) and three-dimensional (3D) solid models. For the latter two cases, calculations were performed using the finite element program ADINA. Results for the 2D model of the specimen were fitted by polynomials for a wide range of specimen geometry parameters and Poisson's ratio values. Considerable differences were observed between the beam model parameters and the 2D or 3D ones. The differences in results for the 2D and 3D models are small and mainly connected with non-uniformity of the SIF distribution along the front of a through-crack in the 3D solid. Results of processing one- and three-point bend test data reported in the literature are presented. Numerical DSIF values are compared with the experimental ones.     

Microstructural Modeling and Second-Order Two-Scale Computation for Mechanical Properties of 3D 4-Directional Braided Composites

This study is concerned with the microstructural modeling and mechanical properties computation of three-dimensional (3D) 4-directional braided composites. Microstructure of the braided composite determines its mechanical properties and a precise geometry modeling of the composite is essential to predict the material properties. On the basis of microscopic observation, a new parameterized microstructural unit cell model is established in this paper. And this model truly simulates the microstructure of the braided composites. Furthermore, the mathematical relationships among the structural parameters, including the braiding angle, fiber volume fraction and braiding bitch, are derived. By using the unit cell model, the second-order two-scale (SOTS) method is applied to predict the mechanical properties of 3D 4-directional braided composites, including stiffness parameters and strength parameters. Besides, the effects of the braiding angle and fiber volume fraction on the elastic constants are investigated in detail. Numerical results show that the predictive stiffness and strength parameters are in good agreement with the available experimental data, which demonstrate that the established unit cell model is applicable and the second-order two-scale method is valid to predict the mechanical properties of 3D 4-directional braided composites.     

可见光与热像融合的三维温度模型重建

热像仪因其能够通过检测物体表面热辐射而产生温度图像,近年来被广泛应用于多种工业场合.然而,由于热像图缺少直观的几何信息,当物体表面温度相近时,难以通过人眼分辨物体特征差异.为了解决这个问题,提出了一种结合可见光几何信息与热像图温度信息的三维模型重建方法.首先使用自制标定板进行可见光相机与热像仪的校正;随后,通过运动恢复...     

Charge Transfer Magnetoexciton at Vertically Coupled Nanorings

We analyze the low-lying energy levels of a charge transfer exciton at vertically coupled coaxial nanorings in the presence of the external magnetic field applied along the axis. In order to assess the experimentally relevant domain of parameters, we adopt a model of a narrow ring for which the 3D wave equation can be reduced in the adiabatic approximation to a simpler 1D model describing a circular rotation of particles with renormalized parameters depending on the morphology of the actual heterostructure. The energies as functions of the threaded magnetic field are calculated and the effect of the nanoring’s morphology and dimension on the Aharonov-Bohm (AB) oscillations, related to the difference between the electron and the hole masses, is analyzed.     

On automated analysis of flow patterns in cerebral aneurysms based on vortex identification

It is hypothesized that the risk of rupture of cerebral aneurysms is related to geometrical and mechanical properties of the arterial wall as well as to local hemodynamics. In order to gain better understanding of the hemodynamical factors involved in intra-aneurysmal flows, a thorough analysis of the 3D velocity field within an idealized geometry is needed. This includes the identification and quantification of features like vortices and stagnation regions. The aim of our research is to develop experimentally validated computational methods to analyse intra-aneurysmal vortex patterns and, eventually, define candidate hemodynamical parameters (e.g. vortex strength) that could be predictive for rupture risk. A computational model based on a standard Galerkin finite-element approximation and an Euler implicit time integration has been applied to compute the velocity field in an idealized aneurysm geometry and the results have been compared to Particle Image Velocimetry (PIV) measurements in an in vitro model. In order to analyze the vortices observed in the aneurysmal sac, the vortex identification scheme as proposed by Jeong and Hussain (JFM 285:69–94, 1995) is applied. The 3D intra-aneurysmal velocity fields reveal complex vortical structures. This study indicates that the computational method predicts well the vortex structure that is found in the in vitro model and that a 3D analysis method like the vortex identification as proposed is needed to fully understand and quantify the vortex dynamics of intra-aneurysmal flow. Furthermore, such an automated analysis method would allow the definition of parameters predictive for rupture in clinical practice.     

Flexible three-dimensional measurement technique based on a digital light processing projector

A new method of 3D measurement based on a digital light processing (DLP) projector is presented. The projection model of the DLP projector is analyzed, and the relationship between the fringe patterns of the DLP and the fringe strips projected into the 3D space is proposed. Then the 3D shape of the object can be obtained by this relationship. Meanwhile a calibration method for this model is presented. Using this calibration method, parameters of the model can be obtained by a calibration plate, and there is no requirement for the plate to move precisely. This new 3D shape measurement method does not require any restrictions as that in the classical methods. The camera and projector can be put in an arbitrary position, and it is unnecessary to arrange the system layout in parallel, vertical, or other stringent geometry conditions. The experiments show that this method is flexible and is easy to carry out. The system calibration can be finished quickly, and the system is applicable to many shape measurement tasks.     

Finite Element Analysis of Mechanical Properties of 3D Four-Directional Rectangular Braided Composites Part 1: Microgeometry and 3D Finite Element Model

Based on the microstructure of three-dimensional (3D) four-directional rectangular braided composites, a new parameterized 3D finite element model (FEM) is established. This model precisely simulates the spatial configuration of the braiding yarns and considers the cross-section deformation as well as the surface contact due to the mutual squeezing in the braiding process. Moreover, it is oriented in the same reference frame as the composites, which coincides with the actual configuration of 3D braided composites and facilitates the analysis of mechanical properties. In addition, the model investigates the relationships among the structural parameters, particularly the braiding angle and the interior braiding angle, which were not taken into account in the previous models. Based on the parameterized FEM, the structural geometry of the composites is analyzed and some conclusions are drawn herein. Good agreement has been obtained between the calculated and measured values of the geometric characteristics of braided composite samples.