以给定的三次Bézier曲线为边界测地线的双三次Bézier曲面构造

曲面上的测地线是曲面上一类重要的曲线。测地线在计算机可视化、图像处理、 服装设计等领域均有广泛应用。该文利用一条曲线为所在曲面的测地线当且仅当它的从切面与 该曲面在这条曲线上的切平面重合这一论断,做了以下工作：对给定的三次Bézier曲线,构造 双三次Bézier曲面,使该曲面以给定的曲线为其边界测地线;讨论了具有给定测地线的组合双 三次Bézier曲面的连续性拼接问题;为了说明所给方法的有效性,给出了几个数值实例。     

旋转面计算机辅助缠绕设计中的拟测地线算法

本文提出了旋转面上的拟测地线的打滑系数计算公式,并可以运用拟测地线样条作缠绕路径设计。从而提出了计算机辅助缠绕设计中的一个稳定,快速的算法－拟测地线算法,该算法充分开发自由度,并能显示装示,增加灵活性,使得整个缠绕过程成为一个统一的,可预先加以控制的操作过程。     

纤维缠绕弯管的线型设计与仿真

提出了一种弯管缠绕线型的设计方法.首先,建立了弯管的纤维缠绕数学模型,在对缠绕线型规律进行分析的基础上,再采用测地线辅助以定位销的纤维缠绕设计方法进行纤维缠绕,实现了弯管纤维缠绕的系统仿真,这种方法克服了传统纤维缠绕模式在缠绕弯管端部时要采用非测地线线型,而只采用测地线再辅助以定位销即可实现弯管的纤维缠绕.仿真结果表明,该纤维缠绕线型设计方案精确可靠,满足纤维缠绕的基本要求,对实际生产有很重要的作用,并为弯管纤维缠绕的应用奠定了理论基础.     

过测地线的优化曲面设计

给定一条曲线,构造以其为测地线的曲面,这是服装鞋帽类产品的设计/制造业中的一个现实课题.已有研究结果是构造出以给定曲线为公共测地线的曲面束,然后用拟合数据点的方法来确定最终曲面.这种通用方法受到曲面参数及其表示方法的影响,且没有对曲面的光顺程度加以考虑.从服装材料的特性和设计思想出发,提出一种利用能量优化来确定最终曲面的新方法.通过改变曲面表示形式和引入能量函数,方便而有效地确定了过给定测地线的一张优化曲面.给出了在插值拟合等约束条件下的相应算法.实例表明,所给算法很好地模拟了成衣的光顺设计与加工,在计算机辅助设计/制造(CAD/CAM)中富有应用价值.     

光滑曲面上的G1插值曲线

在计算机图形学和计算机辅助几何设计中,限制在光滑曲面上保持几何连续的曲线插值技术显现出越来越重要的作用.文中用直纹面投影的思想研究了这一问题,给出了一种在光滑曲面上保持G1连续的样条曲线插值技术.首先构造一条插值曲面上已知点列的空间3次Bézier样条曲线,然后通过一张直纹面将这条空间插值曲线投影到已知曲面上,即可得到限制在已知光滑曲面上的G1插值曲线.理论推导和实例显示表明,该技术具有推广应用的广阔前景.     

三角域上三阶T-Bezier曲面片的构造与设计

在计算机辅助几何设计中,T-Bezier曲线曲面被视为一种新的自由曲线曲面造型工具得到广泛研究,然而其曲面都是张量积形式的,为了进一步研究非多项式空间中的T-Bezier基,完善其关于三角域部分的理论,构造了满足正性、权性、对称性、边界性质和线性无关性的基函数,并证明了三角域上相应曲面的一些性质;最后给出了一些应用。     

在正轴测投影中圆环面上经,纬线圆的数学模型及其计算机实现

推导出了圆环面上经线圆和纬线圆正等测投影的数学模型，并在计算机上得以实现。     

以多条离散曲线为测地线构造离散曲面

为了解决CAD中逆向主动设计问题,提出以任意多条空间离散曲线为测地线构造离散曲面的算法.首先通过密切圆思想离散化曲线相关几何变量;其次利用局部插值思想和测地线蕴涵特征,推导出满足约束条件的离散曲面公式;最后给出以B样条为度量函数的离散曲面构造公式.逆向主动设计实例表明,该算法是可行的并有较强的交互性,可以通过调整B样条度量函数的节点向量或控制顶点来调节曲面形状,设计出满足各种不同需求的曲面,在服装、鞋帽、义齿设计等领域有很好的应用前景.     

准均匀B样条曲面的多分辨率表示及应用

在多分辨率曲线和曲面造型中，B样条小波已经得到了广泛应用。曲线和曲面的多分辨率造型成为一个研究热点。通过阐述准均匀B样条曲线曲面的基于小波分解的多分辨率表示的数学原理，给出了具体的曲线和曲面小波分解算法和实验结果，说明了准均匀B样条曲面多分辨表示的优点及其在工业上的应用。     

用于弯管的计算机辅助纤维缠绕

纤维缠绕模式在计算机辅助纤维缠绕中起着关键的作用,然而对于非轴对称纤维缠绕设计,目前还没有稳定、可靠的模式设计方法.另外,如何有效地处理纤维路径设计中产生的大量数据也是非轴对称纤维缠绕的一大难题.给出了用于弯管的纤维缠绕模式和一种被称为节点存储法的新的数据处理方法.     

Splines in the parameter domain of surfaces and their application in filament winding

For non-axisymmetric filament winding in the composite industry, it is difficult to automatically design fiber paths with uniform distribution, full coverage, and non-slippage. Geodesics and semi-geodesics are commonly used as non-slippage trajectories in the fiber path design. However, the uniqueness of these curves from the initial conditions severely restricts the freedom of design, which plays an important role in producing high performance parts. This paper presents a new class of trajectories with more freedom by generalizing splines, and gives the conditions to make these splines on cylinders and cones stable. The proposed trajectory has been applied to filament winding on elbows. Practical results show that the fiber distribution is excellent, and the finished product has extremely uniform thickness.     

复合材料弯管纤维缠绕路径和机器路径的CAD

提出用于缠绕弯管的纤维路径和机器路径设计的数学原理和方法，并开发了一套设计和制造复合材料弯管的CAD系统．该系统的主要功能如下：(1)设计满足所有缠绕技术要求的稳定纤维路径；(2)生成用于有限元分析的层叠网格数据；(3)生成用于四轴缠绕机的控制数据；(4)纤维路径和机器路径的实时三维仿真．设计出的纤维路径不会产生打滑、架桥等现象，分布均匀．     

Development of Computer Simulation System for the Winding of Toroidal Pressure Vessels

1 Introduction Filament winding is a widely-used manufacturing process in composites industry. Continuous filaments can be oriented to match the requirements of the direction and magnitude of stresses in a laminated structure, allowing reinforcement loading. More recently, filament wound toroidal pressure vessels have emerged as an attractive alternative in aerospace, nuclear, medical appliance and underwater fields where space-saving, weight reduction and non-drift of center of mass are requi…     

Accuracy-speed relationships of a robotic filament winding cell

Filament winding is a process in which tensioned resio-impregnated continuous fibers are placed on specified paths of a rotating mandrel to cover the entire surface thus forming a composite component. Traditionally, filament winding is carried out on multi-saris numerically controlled lathe-like machines. This paper describes the evaluation of a robot based filament winding cell consisting of an industrial robot (ASEA IRB 6/2) and an in-house fabricated mandrel drive mechanism, both being coordinated by a personal computer. As in many manufacturing processes, tradeoffs exist between accuracy and speed. The accuracy vs speed relationships of the robotic winding cell were experimentally determined for discrete, fine and medium movement modes while traversing a segmented delivery eye path for a cylindrical mandrel in three configurations (in-line, offset and angled with respect to the axis of rotation). The results show that the robot winding cell is appropriate for very accurate winding of fiber strands if the mandrel axis is concentric with the mandrel drive axis and the discrete mode (i.e. low speed) of the robot is used. For high speed wet winding all three configurations can be accurately wound in the discrete and fine modes.     

卫星推进系统复合材料高压气瓶爆破失效分析

介绍一种卫星推进系统复合材料气瓶的2种功能失效模式:爆破失效和疲劳失效.重点分析引起爆破失效的主要因素,通过ANSYS采用薄壁壳单元SHELL 91模拟碳纤维螺旋缠绕层和环向缠绕层组合缠绕的多层结构模型,并提出一种爆破失效验证方法.研究结果表明,应力断裂、复合层受损和树脂开裂等是引起复合层破裂的主要因素.复合材料气瓶测试结果表明:采用SHELL 91模拟复合多层结构的分析方法是一种有效、实用的方法;基于复合层单层结构判定理论的爆破失效验证方法是合理、可行的,并可以为降低其失效概率提供数据依据.     

Computer analysis of filament-reinforced metallic-spherical pressure vessels

A computer analysis of filament-reinforced-metallic spherical vessels is presented. The design method uses the load-bearing liner approach and leak-before-rupture as a design criterion. The specific thicknesses of liner and filament composite required to sustain the pressure load are based on the equation of load compatibility and controlled by (1) buckling strength of the metal liner, (2) the maximum strain range for the required operating cycles and (3) the maximum strain capability remaining after cycling. The desirable filament winding pattern is such that the composite has, to the greatest extent possible, uniform thickness and isotropic elastic constants. To account for discontinuity effects, and the slippage between the liner and the composite, the stress and strain levels are best determined using finite element techniques. Aerojet's “AB5U” computer program for axisymmetric bodies having anisotropic material properties is used for the elastic-plastic stress (strain) analysis. Three pre-processor computer programs, “EPCS”, “FIBER” and “REVNOD”, developed by the authors, calculate (from specified filament properties, resin properties, winding pattern, and other geometric data) the necessary input to “AB5U” which includes the geometric data, and elastic constants. A post-processor “POST” was developed to calculate the residual stresses following the proof cycle, the operating strain ranges, and the burst pressure prediction. This capability provides accurate results for use in optimization of the design and enables the analyst to converge quickly to the lightest weight tank possible consistent with specification requirements.     

纤维缠绕机的计算机控制系统设计

从纤维缠绕机的结构和工作原理出发,介绍了纤维缠绕机的控制系统。提出了以计算机为核心的控制系统的硬件组成,并给出了控制程序的设计与运行结果。该控制系统使得缠绕机缠绕工艺有很大的提高。     

Green product design through product modularization using atomic theory

With increasing environmental consciousness and the establishment of environmental protection regulations, green product design not only plays a crucial role in a modern industry but is also becoming the main focus of the future market. In this paper, an innovative method is presented that uses the concepts of atomic theory to solve design modularization problems for green product design. With the developed method, products can be modularized based upon given green constraints, e.g., material compatibility, part recyclability, and part disassemblability. The developed method can help engineers effectively create green designs in the initial design stage, based on product lifecycle requirements. With green considerations incorporated into new modules, a new design can be created that improves upon an original design, with respect to environmental impacts. Product designers can use our method to compare differences between their original designs and the new green modules and then perform necessary design modifications. A table lamp and a motor are used as case study examples to show the effectiveness of the atomic-theory-based green product design method.