Functionally Gradient Material Laser Rapid Prototyping Technique

The functionally gradient material laser rapid prototyping system is developed based on the increasing material manufacture idea of the rapid prototyping. The system hardware is composed of a 5 kW CO₂ laser, a three-dimensional numeric control table, a three-stock-bin coaxial powder delivery device, and an integration operation control desk. The system software is composed of the CAD slicing and scan filling module, materials component distributing design module, and hardware equipment integration drive module. The real time change proportion allocation technique of three metal powders, powder uniform mixing technique, and coaxial powder delivery technique are studied. According to the principle of the output powder cumulative volume invariable in unit time, the real time powder allocation formulae are deduced. The design method of the materials component distributing regularity in the part entity is studied. The gradient change regularity of the face gradient, line gradient, and point gradient is studied. A sort of the file layout of integrating material information and geometry information is brought forward.     

Functionally Gradient Material Laser Rapid Prototyping Technique

The functionally gradient material laser rapid prototyping system is developed based on the increasing material manufacture idea of the rapid prototyping. The system hardware is composed of a 5 kW CO2 laser, a three-dimensional numeric control table, a three-stock-bin coaxial powder delivery device, and an integration operation control desk. The system software is composed of the CAD slicing and scan filling module, materials component distributing design module, and hardware equipment integration drive module. The real time change proportion allocation technique of three metal powders, powder uniform mixing technique, and coaxial powder delivery technique are studied. According to the principle of the output powder cumulative volume invariable in unit time, the real time powder allocation formulae are deduced. The design method of the materials component distributing regularity in the part entity is studied. The gradient change regularity of the face gradient, line gradient, and point gradient is studied. A sort of the file layout of integrating material information and geometry information is brought forward.     

Aerodynamically Assisted Tip-Pen Direct Writing

Scaffolds require individual external shape and well-defined internal structure, which is of great importance for tissue engineering. Rapid prototyping (RP) uses layer-manufacturing strategies to create physical objects and has the advantage on scaffold fabrication. A new RP technology called aerodynamically assisted tip-pen direct writing was developed to construct the complex architectures. Compared with the traditional nozzle, the new nozzle has a micro-tip in the center of the micro-hole. The flow is determined by the gap between the micro-hole and micro-tip, which makes it practical for more accurate flow control. A highly accurate three-dimensional (3-D) micro-positioning system was employed with the new nozzle to deposit maltose structures. 3-D architectures had been made by this method, the width of fiber in which is about 120 μm. The results show that this method provides a possibility to construct 3-D scaffolds with tissue-scale features (i.e., 10–100 μm) without bad influence on the biological activities.     

电偏转抛射式快速成型工艺的仿真

基于电偏转抛射式快速成型(RP)工艺方法是通过电场控制带电颗粒的运动轨迹实现分层截面的成型，作者开发了电偏转的抛射式RP工艺的仿真系统．该仿真系统读入CLI格式的层面数据后，根据分层截面轮廓数据生成工艺规化和扫描路径，控制带电的颗粒进行扫描，并在计算机屏幕上实时模拟显示扫描轨迹及原型件的三维实体成型过程．为电偏转抛射式快速成型工艺的试验研究提供一定的理论依据．     

静电吸附式快速成型制造法

静电吸附式快速成型制造法是一种新的快速成型方法。它的工作原理是：首先产生可吸附粉末黏结材料的带电截面图像，然后，吸附粉末黏结材料并输送到粉末基体材料上，再通过一定方式使粉末黏结材料熔化，把粉末基体材料黏结起来并固化。这种方法是在计算机的控制下，通过逐层成型（一次成型一整层），而不是逐点成型的方式来成型三维物体的，因而，用此方法成型零件，效率高，成本低。     

快速成型制造中的工艺支撑自动生成技术

提出了快速成型制造中的两工艺支撑新形式（向下特征支撑和局部支撑）。针对向下特征支撑形式，提出并实现了基于一维几何元素集合运算的支撑自动生成算法；针对局部支撑形式，提出并实现了基于STL(Stereolithograhy)模型三角面片拓扑分析与空间运算的支撑自动生成算法。结合SL(Stereo Lithography)工艺，进行了带支撑零件的成型。工艺实验证明，提出的工艺支撑自动生成技术不仅可自动地对STL模型添加合理的工艺支撑，而且可实现切片操作和扫描数据生成的融合。该技术可明显提高快速成型系统的加工效率与集成度，同时又降低系统的成本。     

用高精度迎风格式模拟潜入式喷管流场

为了研究固体火箭发动机潜入式喷管内部工质的流动特性 ,首先采用改进的 L U-SGS方法和高精度、高分辨率的 MUSCL TVD格式数值模拟了 JPL美国喷气推进实验室喷管 ,数值模拟结果和实验结果吻合得很好。证明了这种方法可以准确地捕捉到流场中可能出现的各种复杂流动。用同样的数值计算方法模拟了固体火箭发动机潜入式喷管 3个时刻的准三维流场 ,对复杂的计算区域做了分区处理 ,为复杂的边界条件做了简化处理模型。分析了燃烧室潜入段处涡的形成和发展过程以及入口湍流度对喷管的气动参数的影响 ,为设计高性能的固体火箭发动机提供了有益的帮助     

钨极气体保护焊金属原型技术工艺

介绍了基于钨极气体保护焊(GTAW)的金属原型技术成型工艺及其实验系统组成,对GTAW成型过程进行分析,得到了与金属零件成型相关的焊接工艺参数,通过实验与数学建模得到了关键参数(焊接电流、焊接速度、送丝速度)与焊缝几何尺寸的关系,根据快速成型的特点及要求,优化了焊接工艺参数并进行了三维金属零件的堆积实验.结果表明:用该工艺参数制造的金属零件成型较好,表面均匀,能够满足金属原型制造的要求.     

A Study of Melt Flow Analysis of an ABS-Iron Composite in Fused Deposition Modelling Process

Fused deposition modelling (FDM) is a filament based rapid prototyping system which offers the possibility of introducing new composite material for the FDM process as long as the new material can be made in feedstock filament form. Swinburne has been undertaking extensive research in development of new composite materials involving acrylonitrile-butadiene-styrene (ABS) and other materials including metals. In order to predict the behaviour of new ABS based composite materials in the course of FDM process, it is necessary to investigate the flow of the composite material in liquefier head. No such study is available considering the geometry of the liquefier head. This paper presents 2-D and 3-D numerical analysis of melt flow behaviour of a representative ABS-iron composite through the 90-degree bent tube of the liquefier head of the fused deposition modelling process using ANSYS FLOTRAN and CFX finite element packages. Main flow parameters including temperature, velocity, and pressure drop have been investigated. Filaments of the filled ABS have been fabricated and characterized to verify the possibility of prototyping using the new material on the current FDM machine. Results provide promising information in developing the melt flow modelling of metal-plastic composites and in optimising the FDM parameters for better part quality with such composites.     

离心式中间包流场的大涡模拟研究

为了研究离心式中间包的流动过程,采用大涡模拟(LES)方法针对3种不同情况,即(a)电磁力加直水口注流;(b)利用钢液的位能使用弯水口注流;(c)电磁力和弯水口注流共同作用,考察了影响旋流强度和中间包内流动结构的工艺参数.结果表明,LES方法可以成功模拟离心式中间包的三维湍流流场.与单纯电磁力或单纯弯水口相比,旋转电磁力和弯水口共同作用时可使水平面的旋流强度显著增强.在原有电磁力作用的基础上,使用弯水口注流可比原流场最大速度值增加约15%~19%.     

钢液注流的惰性气幕保护系统

对钢液注流的惰性气幕保护系统在实验室进行了冷模拟试验研究。通过向安装在钢包或中间罐水口下方的引流管内吹入惰性气体形成保护气幕 ,使钢流与空气完全隔离 ,防止其发生再氧化 ,减少钢中的非金属夹杂物 ,提高连铸坯质量。     

激光变长线快速成型机控制系统

论述了激光变长线快速成型系统的工作原理和特点，对系统中采用可变长度的激光线段对粉末材料进行有选择地烧结的实现方法进行了说明，着重介绍了其控制系统的软硬件结构．     

陶瓷过滤器脉冲喷吹清灰系统动态模型

针对在使用刚性陶瓷过滤器时难以解决其脉冲喷吹清灰的问题 ,利用气体动力学和流体瞬变理论建立了脉冲喷吹系统内气体流动的动态仿真模型 ,从而解决了由于实际管路内气体为非稳态流动而按稳态方法分析其流场会产生较大误差的问题。将由模型计算出的喷吹气体质量流量与热线风速仪的测定结果进行了对比 ,确定出脉冲阀的时间特性参数。利用该模型分析了储气罐容积、管线长度、喷嘴直径等参数对喷吹气体流动特性的影响。结果表明 ,该模型可用于分析脉冲喷吹系统的结构参数和流动参数对喷吹清灰性能的影响 ,且此模型的建立对气体过滤器脉冲喷吹系统的优化设计具有参考价值。     

基于快速成型制造技术的滴客快速制造方法研究

针对节水灌溉设备中滴管的嵌入式迷宫流道，应用快速成型制造技术进行了滴管的设计及快速模具制度，研究内容包括：应用参数化设计思想进行滴管CAD设计；以精密模具制造技术为核心进行滴管CAD工艺设计和快速模具制造（RT）工艺模型的生成；应用快速成型制造技术进行样件的制备和功能试验，完成了滴管设计的快速试验和修改；进行金属喷涂快速注塑模具的制造，实现了产品和模具设计－验证－制造的集成化。     

3D打印金属材料研究进展

3D打印技术是快速原型制造技术的一种,也被称为增材制造技术,被誉为"第三次工业革命"的核心技术,其中金属3D打印被认为是将来制造业的主导方向.金属粉末材料是金属打印的物质基础,同时也是3D打印技术发展的突破点.综述了3D打印金属粉体材料的研究现状,重点介绍了钛合金、铝合金、不锈钢、高温合金和镁合金等5种金属粉体材料在3D打印技术中的应用,并对金属粉体材料的运用进行总结和展望.     

Effect of Processing Parameters on Thermal Phenomena in Direct Laser Metallic Powder Deposition

Direct laser metallic powder deposition technique is widely used in manufacturing, part repairing, and metallic rapid prototyping. The ability to predict geometrical accuracy and residual stress requires an understanding of temperature distribution during the deposition process. This study presents a numerical model of three-dimensional transient heat transfer in a finite model heated by a moving laser beam. Thermal phenomena in the process were investigated. The complex solid-liquid problem and latent heat of fusion were treated by means of equivalent thermal conductivity and modified specific heat, respectively. Using method of birth and death of elements, the growth of additive layers and the shape of melt pool were obtained. The effect of processing parameters such as absorbed power, travel speed, and preheated temperature on melt pool sizes and cross-section of deposited layer profile was studied. The results show that the melt pool sizes increase with absorbed power and decrease with travel velocity. In addition, the preheated temperature contributes less to the melt pool size. The results are generally in a good agreement with experiments in published literature.     

Aerodynamically Assisted Tip-Pen Direct Writing

Scaffolds require individual external shape and well-defined internal structure, which is of great importance for tissue engineering. Rapid prototyping (RP) uses layer-manufacturing strategies to create physical objects and has the advantage on scaffold fabrication. A new RP technology called aerodynamically assisted tip-pen direct writing was developed to construct the complex architectures. Compared with the traditional nozzle, the new nozzle has a micro-tip in the center of the micro-hole. The flow is determined by the gap between the micro-hole and micro-tip, which makes it practical for more accurate flow control. A highly accurate three-dimensional (3-D) micro-positioning system was employed with the new nozzle to deposit maltose structures. 3-D architectures had been made by this method, the width of fiber in which is about 120 μm. The results show that this method provides a possibility to construct 3-D scaffolds with tissue-scale features (i.e., 10-100 μm) without bad influence on the biological activities.     

反求工程与快速原型集成的复杂曲面产品制造技术

在研究了反求工程的输出接口与快速成型输入接口标准的基础上，提出了一种反求工程（RE）与快速原型（RP）直接集成的复杂曲面产品快速开发的方法，即利用基于断层测量及光学三角形法测量的点云数据直接构造STL（Stereo ithography)模型文件，并输入到LPS（Laser Prototyping System)快速成型系统，直接用于制作产品原型，从而避开了传统反求工程中的复杂曲面重构，因此极大地缩短了这类产品的开发周期，降低了开发成本，数字化动态人体模型快速开发的工程实例表明，该方法比传统曲面建模制造技术的效率提高了55％。     

光固化快速成型过程中零件变形的数值模拟

在对光固化快速成型过程中零件层间相互作用的力学行为进行分析后,提出了以固态降温收缩来模拟液－固收缩伯思想,据此建立的逐层累加的等效力学模型用作有限元分析,可借助ANSYS软件进行加工零件的应力、变形分析和预测,试验结果表明：以该力学模型计算出的结果与试验结果一致,可以很好地模拟光固化快速成型零件的翘曲变形,并由此改进零件的制作方案,如生长方向的选定,支撑的添加等。     

液态金属中气体射流过程数值模拟研究

应用欧拉-欧拉法双流体模型描述液态金属中气体射流搅拌过程的两相流动及气泡分布.采用分别描述气泡和液体湍流的k-ε两相湍流模型,重点分析气泡和液体在流场中的受力,详细讨论了阻力、升力等相间作用力对气泡分布的影响.结果表明,气泡的喷射对熔池起搅拌作用,中心线上入口处气含率最高,进入熔池后迅速下降,到一定高度后下降趋势变缓,在出口附近趋于不变.预测结果和文献中的实验结果进行对比表明,在给出合理的相间作用力模型时,该模型预测值和实验结果符合较好.