快速成形制造中零件制作方向优化ASP工具研究与开发

对快速成形零件制作方向优化问题进行了研究 ,分析了零件制作方向对零件制作质量和制作效率的影响机理 ,针对快速成形制作过程中的变形、台阶效应、过固化现象以及制作时间问题 ,提出了快速成形零件制作方向优化的准则 ,建立了制作方向优化多目标函数 ,提出了采用遗传算法对目标函数进行求解的具体方法。采用SunJ2EE结构体系开发了零件制作方向优化的ASP工具 ,并将该工具成功应用于RP&M网络化服务集成系统中。     

快速成型制作的时间分析及多零件制作的组合布局优化研究

由于快速成型系统的运行成本很高,需要研究缩短零件的制作时间和减小制作成本的方法。基于SOUP600GH光固化成型机,介绍了零件具体的制作过程和制作时间组成,分析了零件制作方向、分层厚度以及激光扫描速度等因素对优化制作效率的影响。通过10组多零件制作实验,对每组单个零件的平均制作时间进行分析对比,指出了多个零件同时制作对提高制作效率的显著作用,进而主要从减少辅助制作时间的角度研究了多零件制作组合布局优化的准则和方法,并用矩形包络简化布置的方法建立了二维布局优化的数学模型。研究表明,多零件制作及其组合布局优化对提高快速成型的制作效率和降低制作成本都具有重要意义。     

光固化快速成形制造时间的影响因素分析

光固化成形是一种基于逐层累加方式发展起来的新的制作工艺，零件的制作时间是成形中需要考虑的关键问题之一。光固化成形零件的制作时间主要是由两部分组成的，一是树脂的扫描固化时间；二是为保证正常加工而增加的辅助时间，辅助时间的减少有助于降低零件制作时间。制作方向的选择也是重要影响因素，通过选择合适的制作方向，可以大幅度减少制作时间；扫描成形参数对成形效率也有很大的影响，较大的扫描间距可以减少光束扫描的往复距离，达到减少制作时间的目的。     

叠层制造中基于混合遗传算法的分层方向优化

给出了叠层制造领域中零件制作方向优化的3种单目标模型，且单目标优化分别以提高原型表面质量、减少支撑和缩短制作时问为目标；单目标优化模型的解集包含了此目标意义下零件的最优、较优分层方向。提出了零件制作方向优化的带权一声模理想点综合决策模型。设计了一种经改进的混合遗传算法，并用其对零件制作方向优化的3种单目标模型及综合决策模型进行了求解。工艺实验不仅证实了提出的个单目标模型及综合决策模型的正确性与通用性，且证明出基于混合遗传算法的分层方向优化算法具有运算快速、可靠等优点。     

激光快速成形中时间效应与零件翘曲性关系研究

研究了激光快速成形中树脂固化过程以及固化收缩滞后于聚合速度的现象 ,提出了收缩完成的时间效应概念 ,通过实物原形制作研究了时间效应对零件翘曲的影响及几种表现 ,并利用时间效应对成形工艺进行了改进 ,使零件翘曲性得到很大的改善。     

基于光固化原型的功能零件制造

本文介绍基于光固化原型的功能零件快速制造的几种主要技术途径，包括用光固化原型作样模仿形加工功能零件、用光固化原型作为消失模进行功能零件的精密铸造和用光固化原型作为样模铸造功能零件，并对各种途径的特点、局限性、成本以及适用范围进行分析。     

基于区域灵敏度及空间多层形貌的车身设计

提出了区域灵敏度分析方法,并通过设定关键区域的区域厚度变量,将灵敏度分析对象由单个零件的厚度变成关键区域的区域厚度变量。提出了基于优化空间重组及灵敏度筛选机制的空间多层形貌优化技术,对零件沿法向正反两个方向进行了结构形貌优化,并将两种方法应用到某车身轻量化设计中。应用实例表明,该方法可以成功地实现关键区域的灵敏度分析,并能大大缩短车辆开发时间优化。     

基于支撑强度可控的数字光处理三维打印工艺优化技术

为了解决数字光处理三维打印制件去除支撑后表面质量受损问题,根据材料固化特性提出支撑强度差异可控的工艺优化方法。建立了制件固化强度与曝光时间之间的数学模型,并通过力学试验进行了拟合及参数因子修正。在三维打印制造过程中通过软件控制系统对零件模型和支撑模型设置不同的曝光时间,实现强度差异可控,从而降低了支撑去除对零件表面的损伤。试验结果表明,采用所提方法去除支撑后零件的表面质量有所提高,且支撑去除效率提高近40%,为提高数字光处理三维打印制件表面质量和精度提供了新的思路。     

理想材料零件RP制造中的生长方向优化研究

对生长方向优化展开讨论，通过综合考虑几何和材料两方面特征的影响，提出了以最小分层数为目标、以零件整体稳定性为约束条件的生长方向优化算法，并利用建立在单纯剖分基础上的理想材料零件CAD数据交换格式，通过实例验证了该生长方向优化算法足以应用在非均匀材料零件的分层制造中。     

稳定性约束的FDM成形零件建造方向优化设计

增材制造(3D打印)零件的建造方向对制造成本、表面质量、建造稳定性等指标有着重要影响。以绕打印平台坐标轴旋转的3个角度描述建造方向，建立了以台阶效应引起的体积误差表征表面质量、以支撑材料体积和零件打印分层数描述制造成本的多目标优化模型，采用多目标进化算法(MOEA/D)分别实现了基于FDM工艺的两种不同复杂程度零件的建造方向优化。针对优化解集中的零件建造方向存在不稳定、数量偏少且分布离散问题，提出一种基于自支撑表面悬空体积的稳定系数指标来量化建造方向的稳定程度。结合对目标函数的连续性改进，重新建立了考虑建造方向稳定性的多目标优化模型并进行有效求解。优化结果表明，改进目标函数的连续性能获得更多优化解，定义的稳定系数指标能有效量化零件建造方向的稳定程度；当稳定系数小于稳定性阈值0.6时，两种零件优化获得的建造方向均能满足零件建造方向的稳定性要求。     

Influence of building orientation on the flexural strength of laminated object manufacturing specimens

This study aims to define the best building orientation for components produced via the Laminated object manufacturing (LOM) technique to enhance their flexural performance. Results of previous research show that components produced via LOM are capable of with-standing higher deflections than components produced through other layer manufacturing techniques. However, the relation between the building orientation and flexural strength of components has not yet been assessed. Four types of specimens have been manufactured using different building orientations for each type. The specimens have been tested in a machine with four loading points to evaluate their failure mode and identify the best building orientation toward flexural loading. The best building orientation in terms of maximum load before failure is 45°. Furthermore, a repetitive failure pattern is found for each tested condition. Building orientation is confirmed to be a relevant parameter in LOM manufacturing by influencing the mechanical properties of components.     

PART BUILDING ORIENTATION OPTIMIZATION METHOD IN STEREOLITHOGRAPHY

Aiming at the part quality and building time problems in stereolithography (SL) caused by unreasonable building orientation, a part building orientation decision method in SL rapid prototyping (RP) is carried out. Bringing into fall consideration of the deformation, stair-stepping effect, overcure effect and building time related to the part fabrication orientation, and using evaluation function method, a multi-objective optimization model for the building orientation is defined. According to the difference in the angles between normal vectors of triangular facets in standard triangulation language (STL) model and z axis, the expressions of deformation area, stair-stepping area, overcure area are established. According to the characteristics in SL process, part building time is divided into four sections, that is, hatching scanning time, outline scanning time, support building time and layer waiting time. Expressions of each building time section are given. Considering the features of this optimization model, genetic algorithm (GA) is used to derive the optimization objective, related software is developed and optimization results are tested through experiments. Application shows that this method can effectively solve the quality and efficiency troubles caused by unreasonable part building orientation, an automatic orientation-determining program is developed and verified through test.     

A unit sphere discretization and search approach to optimize building direction with minimized volumetric error for rapid prototyping

As a material-additive process, rapid prototyping (RP) has shown its capability in creating complex geometries that traditional material-removal processes cannot accomplish. However, its layer manufacturing nature still subjects itself to undesired staircase effects. It has been shown that staircase effects have relationship with the building orientation in RP processes. In order to minimize staircase effects, the building orientation has to be properly selected prior to the implementation of RP processes. This paper presents a method to select the optimal building direction in RP processes that leads to the minimized volumetric error. In order to explore the global directional space, a unit sphere is uniformly discretized first to represent the potential directions in a 3-dimensional (3-D) space. Following that, each facet comprising the STL geometric model is mapped onto the discretized unit sphere as a great circle individually, which represents the optimal directions for that facet. In order to find the globally optimal solution, both an exhaustive search and a genetic algorithm (GA)-based searching strategy are presented to identify the globally optimal direction for building the 3-D geometry. At the end of the paper, examples are presented to show the effectiveness of the method.     

摄影测量的动态测量应用

摄影测量技术是通过空间交会的原理计算出空间点的三维坐标.借助于高精度的照相机和快速图像处理器,摄影测量可以实现对多点的实时测量监控,从而计算出被测物的姿态、位置、形状以及它们的变化.通过数学建模,分析了摄影测量的动态测量原理,包括仪器部件坐标系的建立,活动部件坐标系的动态跟踪.并以比利时KRYPTON产品为例,介绍了典型摄影测量系统的应用技术,以及它们在航天航空汽车制造等领域中的应用实例.     

A software program for semi-automated measurement of building façades

The dimensions of façades and window openings in buildings are usually determined by direct measurements using tapes and plummets. In this paper, we present a semi-automated application that makes it possible to obtain building measurements by means of an indirect method based on close-range photogrammetry. This application is intended to be used with a single planar-surface measuring system that permits measurements to be made without contact with the building. This system combines the output from a digital off-the-shelf camera and a laser distance meter. These data are used within our application for image orientation and scaling. Next, the software permits calculation of the dimensions of elements on the planar façade and also provides an estimate for the precision of those dimensions. This indirect approach avoids time-consuming and risky procedures in building measurement and permits the user to take inventory of a building under construction.     

超声波定位系统的参数研究

在许多超声波测距系统中,精确地确定电路系统的延时参数是提高测距精度的关键,应用最小二乘的数学方法可以精确地获得超声波信号在电路中的传播时间,有效地提高系统测距精度,在某个物体定位系统中得到了成功的应用。     

跟踪窗口自适应的Mean Shift跟踪算法

目的：针对传统Mean Shift跟踪算法中当目标发生形变时因跟踪窗不能动态改变导致跟偏甚至跟丢的缺陷,提出了一种新的跟踪窗口大小和方向自适应的改进算法。方法：首先采用跟踪窗口内协方差矩阵的主分量分析方法来计算跟踪目标的方向和尺寸大小;然后联合相似性度量和卡尔曼滤波器来更新跟踪窗口。结果：实验证明,本算法针对不断旋转和缩放的运动目标仍能对其进行准确实时的跟踪。结论：改进算法能够满足非刚体目标跟踪系统的要求。     

Impact collapse characteristics of CF/Epoxy composite tubes for light-weights

This paper investigates the collapse characteristics of CF/Epoxy composite tubes subjected to axial loads as changing interlaminar number and outer ply orientation angle. The tubes are aften used for automobiles, aerospace vehicles, trains, ships, and elevators. We have performed static and dynamic impact collapse tests by a way of building impact test machine with vertical air-compression. It is fanad that CF/Epoxy tube of the 6 interlaminar number (C-type) with 90° outer orientation angle and trigger absorbed more energy than the other tubes (A, B and D types). Also collapse mode depended upon outer orientation angle of CF/Epoxy tubes and loading type as well ; typical collapse modes of CF/Epoxy tubes are wedged, splayed and fragmentcl.     

MACHINING STUDIES OF UD-FRP COMPOSITES PART 2: FINITE ELEMENT ANALYSIS

A number of parameters and an exhaustive material development and experimental procedure to determine the response variables like cutting forces, surface damage restricts the expensive experimental research. In this context, Finite Element Method (FEM) analysis can be used as a tool for the prediction of the various machining responses. A finite element analysis of the orthogonal machining of Uni-directional Glass Fiber Reinforced Plastic (UD-GFRP) laminates is presented in this study to understand the complex relation between fiber orientation, tool geometry, depth of cut on cutting forces and sub-surface damage.