基于全自动热喷涂技术的电力设备零部件涂层制备工艺研究

变电设施常常服役于空气环境中,容易受到腐蚀的影响,对设备进行表面改性处理可以大幅改善设施的防腐蚀性能,提升其使用寿命。全自动热喷涂技术作为一种新型表面改性方式,是通过热源将合金加热至熔融或半熔融状态并涂覆与基体表面的技术。本文对其工艺参数进行了系统研究,发现当喷涂速度为0.1m/s,涂层厚度最大(700μm)、孔隙最小(2.1%)、性能最佳。喷涂距离对涂层孔隙率的影响较大,在距离为180mm,孔隙率达到最低(4.3%),此外还可根据对涂层厚度需求以及孔隙率的大小选择合适的喷涂电压和电流。对最佳参数条件下热喷涂铝涂层的试样进行盐雾试验。发现涂层表面会发生氧化腐蚀,生成以Al(OH)₃为主的腐蚀产物并在涂层表面形成致密的氧化膜。此外,产生的腐蚀产物还可以填补热喷涂过程中形成的孔隙,阻止腐蚀介质继续向涂层内部渗入。     

一种排样图像轮廓线生成方法

针对传统基于聚合的多边形拟合法对皮革图像边缘毛刺敏感和对所围面积无法控制的问题,提出了一种排样图像的轮廓线生成方法。该方法通过将距离误差由绝对值改为带符号值,并对非利用面积误差施加约束,使获得的排样轮廓线既抑制了毛刺的干扰,又是真实轮廓线的最大内接多边形,皮料面积得到了充分利用。实例计算和应用结果表明了本文方法的有效性和科学合理性,且对其他工业排样问题也具有一定的参考价值。     

甲烷浓度对硬质合金微型立铣刀表面生长 金刚石涂层的影响

金刚石涂层的应用可显著提升刀具使用寿命.文章采用钽丝为热丝,氢气、甲烷为反应气体,通过热丝气相沉积法在不同甲烷浓度下对硬质合金立铣刀表面进行沉积金刚石涂层.通过扫描电子显微镜、拉曼光谱对不同甲烷浓度下金刚石涂层的表面形貌、涂层质量进行分析.结果显示,随着甲烷浓度增加,涂层中二次形核率增加、金刚石晶粒尺寸变小,金刚石晶粒能够完好地嵌入到硬质合金表面形成机械锁扣结构,提高膜-基结合强度,但过高的甲烷浓度使得活性氢原子对石墨的刻蚀强度减弱,使得涂层中金刚石晶粒晶界处非金刚石碳相含量逐渐增加,涂层质量下降.当甲烷浓度为3%时,硬质合金立铣刀表面金刚石涂层结晶度高、晶粒间接触紧密、涂层中非金刚石碳相含量低、膜-基结合强度高,端刃处未出现涂层剥落现象.文章工作有助于理解热丝气相沉积法中碳源浓度对表面金刚石涂层沉积效果及涂层失效的影响,使硬质合金立铣刀表面金刚石涂层沉积工艺得到进一步优化.     

一种由轮廓线重建物体表面的方法

针对基于轮廓线拼接重建物体表面所出现的轮廓对应和分叉问题,提出了一种通过体数据转换由轮廓线实现重建物体表面的方法。在分析体数据构造中出现逼近精度问题的前提下,通过提高轮廓线上点的密度,生成精确度较高的体数据。该方法通过对相邻层轮廓线区域的集合运算,只对处于集合运算解中的像素点进行距离函数值的计算。采用MC（Marching Cubes）算法生成等值面,完成物体的表面重建。实验结果表明,该方法能顺利解决基于轮廓线拼接重建物体表面中出现的轮廓对应问题和分叉问题,既提高重建表面精确度,又加快整个表面的重建速度,是一种可行的方法。     

热处理工艺对硬质合金表面金刚石薄膜 附着性能的影响

文章针对提高硬质合金刀具金刚石涂层结合力问题,提出了一种热处理和酸处理相结合的预处理工艺,详细研究和分析了800~1000℃ 范围内,热处理温度变化与硬质合金刀具表面形貌、金刚石涂层质量、涂层与刀具间附着力之间的关系.热处理工艺显著降低了生长过程中钴对金刚石涂层石墨化的催化作用,进一步提高了碳化钨颗粒的比表面积及金刚石二次形核密度,得到的金刚石涂层晶粒尺寸及压应力较小.过高的热处理温度虽然可以细化基体表面,增加基体与金刚石涂层之间的"机械锁合"作用,但预处理过程中残留在基体表面的深坑却不利于金刚石涂层附着力的提高,在外力的作用下容易在深坑附近产生微裂纹.实验结果显示,在氩气气氛中,900℃ 时热处理的硬质合金基体表面生长的金刚石涂层质量和附着力最佳.     

由任意形状轮廓线重建三维表面的方法研究

由一组二维轮廓线重建出物体的三维表面是医学数据可视化的一种主要绘制方式。当轮廓线比较复杂,例如当遇到非凸轮廓或相邻层轮廓线相差过大时,常用的三角化拼接方法就会失败。文章提出一种新的轮廓拼接方法能够处理任意形状的轮廓线。该方法的基本思想是对轮廓线进行凹凸性层次分析,然后将相邻轮廓线从外到内逐层拼接,从而构成一个三角化的物体表面。实验结果表明,该算法对于手动勾画和自动提取的轮廓线都可以给出较好的重建效果。     

利用电化学阻抗技术测试界面污染对涂层防护性能的影响

本工作采用交流阻抗技术与腐蚀电位监测,研究低碳钢基体表面污染面积(NaCl盐水污染)对醇酸清漆在0.5mol/LNaCl水溶液中防护性能的影响,并探讨有机涂层的失效机制。实验表明基体表面处理的好坏对有机涂层防护性能有着至关重要的影响。基体表面污染,不仅会削弱有机涂层的防护性能,而且能够加速涂层失效过程。     

一种辅助轮廓线的断层医学图像三维重建算法

针对轮廓线重建过程中的轮廓分叉问题,提出了一种改进的多轮廓线三维重建算法,通过构造辅助轮廓线将多轮廓线的连接转换为单轮廓线的连接,改进了利用多轮廓线进行三维重建的不足,利用可接受表面实现特征点的三角化,并根据曲率的变化拟合重建过程中的不光滑表面,进而实现断层医学图像的三维重建。实验结果证明,运用本算法在保证重建物体正确的同时,缩短了体数据的构造时间,加快了整个表面的重建速度。     

TMAH腐蚀液制作硅微结构的研究

通过各向异性腐蚀硅微结构工艺,研究了四甲基氢氧化铵(TMAH)腐蚀液的特性,包括硅(100)晶面腐蚀速率与TAMH溶液浓度、温度、pH值以及过硫酸铵添加剂的关系,并采用原子力显微镜研究了不同腐蚀条件下硅的表面形貌,研究表明:随TMAH溶液的浓度的降低和腐蚀温度的提高,腐蚀速率提高,硅腔的表面粗糙度增大;过硫酸铵添加剂明显改善了硅微腔的表面平整度.本研究所确定的最佳腐蚀工艺条件为:溶液中TMAH浓度为25%,过硫酸铵添加剂浓度为3%,腐蚀温度80℃.在此工艺条件下腐蚀出了深度为230 μm、表面粗糙度小于50 nm的硅微腔.     

(100)硅各向异性腐蚀中残留物的研究

<正> 在硅的各向异性腐蚀工艺中获取平整而光滑的表面至关重要。与联氨水溶液或氢氧化钾水溶液相比,乙二胺-邻苯二酚水溶液(简称EPW)对(100)硅的腐蚀表面更为平整光滑,但当一定量的EPW溶液腐蚀了相当量的硅以后,在被腐蚀表面上尤其在其边角处可能出现一种白色残留物的沉积,由此而破坏被腐蚀硅表面的平整度和光滑度,该种残留物是不同于     

钣金件中匹配孔的半径差及轴线重合度自动检查

摘 要：针对汽车钣金件中匹配孔的半径差及轴线重合度人工检查效率低、易遗漏等问题, 提出了钣金件中匹配孔的半径差及轴线重合度自动检查方法。首先将获得的 B-Rep 三维模型以 面壳封闭的方法拓扑分解为面基本单元;其次根据圆柱面具有 2 条半圆弧线和 2 条直线的特征 对圆柱面进行筛选,并以其为基本单元对圆孔和槽孔进行提取;然后分别获取圆孔和槽孔的半 径及轴线,并利用点到点和点到线距离方法,根据孔匹配原理对匹配孔进行检查分析;最后对 半径差不满足要求和轴线不重合的孔对进行标注。借助 CATIA 的 CAA 开发平台对相关算法进 行了系统设计,并验证方法的可行性。实例检查结果表明,该方法能够高效、准确的对钣金件 中匹配孔的半径差及轴线重合度自动检查。     

钣金件自动展开新方法

在对钣金件特征研究和"零厚度"假设的基础上,提出一种钣金件自动展开新方法.对钣金件进行特征分类,基于特征设计进行钣金件特征造型,并通过特征树的形式存储特征之间的关系,最后对特征树进行中序遍历得到钣金件的展开图.并将上述方法应用在SMCAD(Sheet-Metal CAD)系统中.结果表明,该方法能方便快捷的实现钣金件自动展开,并使钣金件设计和展开摆脱了对三维平台的依赖,展开过程更为简洁.     

基于关键特征相对位置关系的钣金零件检索算法

针对二维钣金类CAD零件相似性的检索,提出一种适用于钣金展开件的相似性检索算法.在分析钣金零件形状特点的基础上,选取设计过程中常用的36种关键特征,建立了关键特征的位置关系模型.该模型以构建关键特征之间的相对位置三角形为基础,具有坐标系无关和旋转无关的特性;以关系模型为依据,提出了钣金件关键特征的相对位置检索算法,并通过实例计算了不同钣金零件之间的相似度.实验结果表明,文中算法是有效的,可满足钣金零件的检索要求,具有实用价值.     

Smart metal sheets by direct functional integration of piezoceramic fibers in microformed structures

Microassembly of piezoceramic fibers in micro cavities at the surface of sheet metal is a novel approach for high volume production of smart adaptronic structural metal parts. In this paper a technology, manufacturing processes and characterization results of metal sheets with an active piezo-metal substructure based on directly integrated piezoceramic fibers are described. The processes include micro-milling of cavities in sheet metal, precision grinding of piezoceramic fibers, PECVD insulating layers with high dielectric strength, microassembly and force-locked joining by forming. In experiments, measurements of the surface roughness and geometric parameters of the piezoceramic fibers and micro cavities were performed. Further, the electrical properties of the insulation coatings were measured. The sensor function of the piezo-metal substructure was proven by a mechanical excitation resulting in a proportional measured sensor signal.     

Three‐dimensional localization of thin‐walled sheet metal parts for robotic assembly

This article presents a technical demonstration of a system for determining the three‐dimensional spatial location of complexly shaped, thin‐walled sheet metal parts grasped by robots during assembly. For successful part assembly, the precise location of grasped parts (essential for successful mating of parts) must be achieved. A localization system is implemented to determine the accurate position and orientation of a sheet metal part that has been picked up by a robot from an arbitrary location. The proposed localization system employs a novel sensing method, utilizing laser‐based proximity and edge detectors, to extract the part feature data in real time. These geometrical feature data are incorporated into an existing localization algorithm, which is based on the singular value decomposition formulation of the part localization problem. The sensing method is particularly effective in measuring 3‐D feature geometry (i.e., thin edges) of sheet metal parts. An experimental single‐robot test bed has been developed to demonstrate the feasibility of the part localization concept for a single sheet metal part. The experimental results obtained from the test bed demonstrate that the system can be effectively used for the localization of thin‐walled sheet metal parts. © 2002 Wiley Periodicals, Inc.     

Automatic recognition of features from freeform surface CAD models

This paper reports the design and implementation of a system for automatic recognition of features from freeform surface CAD models of sheet metal parts represented in STL format. The developed methodology has three major steps viz. STL model preprocessing, Region segmentation and automated Feature recognition. The input CAD model is preprocessed to get a healed and topology enriched STL model. A new hybrid region segmentation algorithm based on both edge- and region-based approaches has been developed to segment the preprocessed STL model into meaningful regions. Geometrical properties of facets, edges and vertices such as gauss and mean curvature at vertices, orientations of facet normals, shape structure of triangles, dihedral edge angle (angle between facets), etc. have been computed to identify and classify the regions. Feature on a freeform surface is defined as a set of connected meaningful regions having a particular geometry and topology which has some significance in design and manufacturing. Feature recognition rules have been formulated for recognizing a variety of protrusion and depression features such as holes, bends, darts, beads, louvres, dimples, dents, ridges/channels (blind and through) etc. occurring on automotive sheet metal panels. The developed system has been extensively tested with various industrial sheet metal parts and is found to be robust and consistent. The features data can be post processed and linked to various downstream CAD/CAM applications like automated process planning, sheet metal tool design, refinement of FEM meshes and product redesign.     

加速度约束下薄板的路径规划的遗传算法研究

研究了薄板在冲压输送过程中的路径规划的遗传算法,该优化算法充分考虑速度、加速度在运动过程中时柔性薄板件的位移、应力的影响.路径上各点的位置坐标和相应各点的加速度值组成浮点数编码,采用罚函数法处理约束问题,并通过构造适当的适应度函数和对遗传算子的选择等得到优化问题的全局最优解.对某一冲压生产线中的薄板在压机与穿梭小车间的传输路径进行仿真实验,实验结果表明,该算法是有效的.     

Dynamic modeling and control of a multi-robot system for assembly of flexible payloads with applications to automotive body assembly

The field of multi-robot control has almost exclusively addressed issues that are of relevance to the manipulation of payloads that are rigid. A number of studies have examined the multi-robot manipulation of rigid payloads with one or more lower-pair joints such as hand tools, i.e., pliers. In this work, we examine certain modeling and control aspects associated with the assembly of flexible payloads with a multi-robot system. While this particular problem is of a general nature, our work is motivated by the particular problem presented by the assembly of automotive bodies from sheet metal parts. State of the art assembly of automotive bodies involves the use of a great number of costly hardware fixtures that are used to orient and clamp each piece of bent sheet metal prior to robot welding. Currently under development, a new assembly technology called flexible fixtureless assembly is being designed to replace fixtures with robotic technology. Each robot grasps one piece of sheet metal, and correctly positions and orients the part to mate them to permit a third robot to weld them. The assembly process is complicated by the fact that the sheet metal parts are flexible, cannot be permanently deformed during mating and must be positioned to within a relatively small position tolerance. This article describes work performed to model the dynamics of a multi-robot system consisting of two robot manipulators bringing sheet metal parts of an automotive body into contact. This dynamic model is used as a tool to facilitate the investigation of control strategies for the execution of this task. To adequately model the system, the sheet metal parts are first discretized into finite shell elements. The flexible payload dynamics are derived via the Lagrangian formulation and combined with the robot dynamics to form one robot-payload system. The system equations are first simplified by making use of some of the properties of the assembly process. This allows certain of the interaction effects between flexible and rigid body coordinates to be ignored. Contact between the sheet metal payloads during the mating process is modeled with an exponential barrier function. Application of Guyan reduction leads to a lower order dynamic model of the sheet metal payloads and a simplified dynamic model of the two robot system suitable for numerical simulation. The model developed is then used to investigate several candidate control methods for the mating of two sheet metal parts. Simulation results are presented for proportional and derivative control with gravity compensation, computed torque control, and master slave hybrid position force control. Simulation results reveal that all three control methods are able to achieve contact force and position stability. Adequate performance of the proportional and derivative control demonstrates that standard industrial controls implemented in commercial robots may be used to control robots for fixtureless assembly tasks. © 1996 John Wiley & Sons, Inc.     

Non-Synchronous Deformation Effect of Particle in Sheet Metal Forming Process

A new concept referred to the non-synchronous deformation effect of particle in sheet metal forming is proposed. The results of finite element analysis show that the flow resistance of sheet metal can be effectively reduced and thus the forming property can be greatly improved if the moving and deformation state of the neighboring elements with equal perpendicular distance to the entrance contour of die is non-synchronous. Experiment tests are presented and the results agree well with FEA simulation. In addition, the mechanism of the non-synchronous effect is analyzed in detail.     

Flexible fixturing and automatic drilling of sheet metal parts using a robot manipulator

The design of robotic system for sheet metal drilling is presented. The machining of sheet metal aerospace parts is currently done manually with the aid of precision drill templates. The drilling template serves two purposes: it locates the drill bit relative to the work surface, and bears the dynamic loads of the drilling process. In the developed system, the template is eliminated by decoupling these tasks. First, an end effector is designed for the drilling task and is positioned using a six degree of freedom robot. Second, the accuracy is improved through the use of active end point recalibration. Dynamic loading of the arm is reduced by making the drilling end effector a jig hand that is preloaded against the workpiece. The developed system is presented and the resultant performance is evaluated through analysis and experiments.