导电性光固化树脂结合剂锯片的研制

采用光固化树脂作为结合剂制作金刚石锯片是近年来快速制造领域里的一个新型制造工艺,针对各种材料进行的切割试验也验证该项技术的可行性和实用性。在使用过程中发现锯片的导电性是一个非常重要的性能要求。对高分子材料的导电性研究进行比较,分析几种不同的实现光固化树脂导电性的途径,找出适合光固化树脂结合剂锯片的有效方法。通过采用镀铜金刚石作为磨料并适量添加导电铜粉,利用试验手段调整配方,最终达到了在光固化树脂结合剂超薄锯片的制造中实现具有导电性的目的。     

Effect of nanosized alumina fillers on manufacturing of UV light-curable-resin bond abrasive tool

As one of the rapid prototyping technologies, ultraviolet-curable resin (UV-resin) curing was recently introduced into the manufacturing of resin bond abrasive tools. This research was conducted to evaluate the influence of nanosized alumina filler on the manufacturing of UV-resin bond diamond grinding wheel, and comparatively study the machining performance of filler-loaded and filler-unloaded tools. The UV-resin and diamond abrasive grains were prepared with nanosized alumina filler in a proportion of 0, 2.5, 5.0, 7.5, and 10 wt%. The cure depth, hardness, and tensile strength of the cured mixture was studied, and the interfacial bond between the diamond grain and cured resin matrix was investigated as well. Two UV-resin bond diamond grinding wheels were fabricated to examine the influence of filler loading on wear performance of the tools. Experimental results based on ceramic workpieces showed that the introduction of alumina filler improved not only the material properties of cured resin matrix but also led to a significant improvement on the abrasive machining performance of grinding wheel.     

Wear of the blade diamond tools in truing vitreous bond grinding wheels: Part I. Wear measurement and results

The wear of stationary blade diamond tools used to generate a precise and intricate form on the vitreous bond grinding wheel is presented. Two types of blade tools made of rod and particle diamond were used. A method to measure the wear of the blade diamond tool in the μm-scale range using the size difference of two parts ground before and after truing was introduced. Two sets of experiments with four truing feeds and four tool traverse speeds across the grinding wheel were conducted on the rod and particle blade diamond tools, respectively. Experimental results showed the wear rate of blade diamond tools was improved at higher truing feeds and traverse speeds due to the brittle fracture of the abrasive and vitreous bond.     

Wear of the blade diamond tools in truing vitreous bond grinding wheels: Part II. Truing and grinding forces and wear mechanism

Truing and grinding forces and the wear mechanism of particle and rod diamond blade tools used to generate precise and intricate forms on rotating vitreous bond silicon carbide grinding wheels are presented. A Hall effect sensor was used to measure the change of grinding spindle power during truing and grinding. A signal processing procedure was developed to identify individual truing passes and to extract the average, peak-to-valley, and standard deviation of the variation of truing force for each pass. The truing force data and SEM micrographs of worn surfaces on blade tools reveal micro- and macro-fracturing of the diamond. The attritious and erosion wear of the diamond rod and particle, erosion of the metal bond, and pulling-out of the diamond particle are also identified. Grinding force data shows that, for the same truing parameters, a wheel trued by the rod diamond blade tool has higher grinding forces than one trued by a particle diamond blade tool.     

Fundamental study and theoretical analysis in a constrained-surface stereolithography system

Stereolithography (SL) technology can be classified into two types, free-surface and the constrain-surface SL systems. Constrain-surface stereolithography (SL) systems have the advantages of resin savings, reduced cost and better layer thickness control. However, the material properties of the curing process and the fabrication parameters need to be determined and optimal process parameters should be found using numerical analysis in order to eliminate trial and error. This paper reports some fundamental experiments that have been conducted in order to explore the curing properties of the resin NAF202 in an E-DARTS system. In addition, a theoretical analysis of the photopolymer curing process in the E-DARTS system has been proposed. A dynamic finite element simulation code with weight function was developed to model the point-by-point curing process in a constraine-surface SL system. A simple implementation to evaluate the developed program is presented, indicating that the proposed program can simulate the shrinkage analysis in accordance with path planning.     

Curing Characteristics of the Photopolymer Used in the Solid Laser-Diode Plotter RP System

Most stereolithography (SL) processes employ ultraviolet (UV) or diode pumped solid state lasers to cure the associated photopolymer to build a 3D part. A UV or diode pumped solid state laser is more expensive in initial cost and maintenance than a semiconductor laser. A semiconductor laser is used in the solid laser-diode plotter (SLP) rapid prototyping system to cure a specific photopolymer (DF2000). The DF2000 photo-polymer is formulated from a based resin, hardening agent, and powder. The wavelength of the semiconductor laser used in the SLP system is 680 nm and is in the range of red colour light. In this work, the curing effect of the visible wavelength spectrums generated by a lamp on the DF2000 photopolymer was investigated, using differential scanning photo calorimetry (DSPC). The DSPC result indicates that the curing degree of the photopolymer using blue light is better than that when using red light. The result also seems showing that the shorter the wavelength, the better the curing effect of the photopolymer. Hence, a blue semiconductor laser (405 nm) or a shorter wavelength laser or even a higher-power lamp, instead of a red laser, can be employed to increase the curing degree of the photopolymer used in the SLP system. The quantitative effect of the SLP processing parameters on the curing degree of DF2000 photopolymer and the mechanical property of the SLP test specimen was studied using the Taguchi method. The results show that the mechanical property of a fabricated part is proportional to the curing degree of the photopolymer. The results also indicate that the scanning pitch of processing parameters is the most sensitive parameter of the SLP system affecting the curing degree and, hence, also affecting the mechanical property. Therefore, the curing characteristics of the photopolymer used in SLP system could be used as an index of the mechanical property of a fabricated part. Also, the employment of a shorter wavelength laser rather than red laser can further improve the part mechanical property and fabrication speed of the part.     

镍铁合金电沉积金刚石工具的研制

提出了采用镍铁合金作为电沉积金刚石工具结合剂的构想。通过分析研究 ,确立了工艺方案 ,对影响镍铁合金沉积层质量的主要因素进行了分析 ,优化了底层沉积、上砂沉积以及加厚沉积时的镀液温度、阴极电流密度等。金刚石套料钻的研制成功 ,证实了镍铁合金作为电沉积工具结合剂的可行性。     

金刚石砂轮刀片划切过程仿真研究

对金刚石砂轮刀片进行力学分析,得到砂轮刀片切向应力与径向应力。应用有限元分析软件ANSYS建立砂轮刀片模型,分别对应8000～32000r/min不同转速下的砂轮刀片,应用第三强度理论,得到不同转速下砂轮刀片的等效应力云图。由仿真结果可以看出,砂轮刀片切向应力大于径向应力,切向应力的最大值发生在砂轮刀片孔壁处,随着转速的提高,砂轮刀片的最大等效应力呈增长趋势。本文为研究划切时金刚石砂轮刀片的性能打下基础。     

电磁耦合无级变速器的调磁及效率分析

详细分析了电磁耦合无级变速系统的工作原理及其调磁原理,在此基础上,利用有限元法对其进行二维有限单元和三维有限单元的分析,研究了电磁耦合无级变速器的磁场的相关特性及调磁对气隙磁场的影响。根据调磁对气隙磁场的影响,计算得出调磁对该系统效率的影响,研究结果为电磁耦合无级变速系统的控制策略及控制系统开发提供了基础。
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<Emphasis Type="Bold">Curl Distortion Analysis During Photopolymerisation of Stereolithography Using Dynamic Finite Element Method</Emphasis>

Stereolithography is one of the rapid prototyping processes which uses a photopolymer as the raw material to build prototypes. The photopolymer absorbs energy by selective laser exposure. The curing effect starts when the absorbing energy exceeds a critical value, and the process is called photopolymerisation. The photopolymerisation changes the phase from liquid to solid. The cured volume can expand and then shrink on cooling. The process parameters such as the scanning speed, scanning path, scanning pitch, and the slicing thickness, lead to different shrinkage and curl distortion, so, the photopolymerisation process is a dynamic material behaviour. In this study, a dynamic finite element simulation code has been developed to simulate the photopolymerisation process. The simulated result for a suspended beam which corresponds to the process parameters shows that a short raster causes less curl distortion than a long raster. The experimental result agrees very well with the simulated result.     

光固化树脂结合剂锯片结合机理及其应用研究

探讨了光固化树脂磨具不同于普通树脂磨具的结合机理，并在该理论的基础上寻找出改善磨具结合性能的措施。首次在光固化树脂结合剂锯片中引进几种金属镀覆的金刚石磨料，通过对不同半导体材料进行切割试验，证实了在光固化树脂结合剂锯片中采用金属镀覆金刚石磨料后，针对单晶硅、铌酸锂、陶瓷等半导体材料，几种不同锯片的磨损率分别降低了259／5～200％、12．5％～62．5％和10．5%～52．6％，加工效率和使用寿命有了显著的提高。     

动态优化刮刀速度的新型涂层工艺

为提高活塞式无扰动涂层工艺的涂层质量,针对高分辨率激光快速成形系统涂层工艺中存在的涂层厚度随制件高度增加而变厚的问题,提出在制作过程中动态优化刮刀速度的涂层方法。研究刮刀速度、制件高度对涂层厚度的影响。采用面响应法,建立涂层厚度误差关于制件高度及刮刀速度的数学模型。根据该模型,在制作过程中随制件高度的变化,动态优化刮刀速度,实现涂层厚度均匀化。验证试验结果表明：与普通涂层工艺相比,新型涂层工艺将涂层厚度偏差由27 μm降为6.9 μm,解决了涂层厚度随制件高度增加而变厚的问题,实现涂层厚度的均匀化,提高堆积方向的制作精度。该涂层工艺也可应用于普通光固化激光快速成形系统中,解决制作陷阱结构时涂层厚度随制件高度变厚问题,因此该工艺对于光固化快速成形技术中提高堆积方向制作精度具有重要意义。     

用于电沉积工具的镍铁合金结合剂工艺研究

基于将镍铁合金用作电沉积工具结合剂的构想,对镍铁合金的电沉积工艺进行了研究,分析了镀液温度以及电流密度对沉积层性能的影响,对各参数进行了初步优化,为镍铁结合剂金刚石工具的研制提供了理论依据     

基于修整力的树脂结合剂金刚石砂轮机械修整

研究了树脂结合剂金刚石砂轮修整过程中修整力与修整效果的关系,基于修整力的变化表征了砂轮的表面形貌及磨削性能。首先,对碳化硼、碳化硅、白刚玉3种砂轮修整工具进行实验,并采集了修整过程中修整力的变化;然后,利用白光干涉仪观测修整后砂轮的表面形貌;最后,对修整后砂轮进行磨削验证实验,得到不同修整工具修整后砂轮的磨削性能。基于上述实验,分析并验证了修整力的变化与砂轮表面形貌和砂轮磨削性能的关系。结果表明,法向力Fn能够表征砂轮的磨粒切削刃密度以及磨粒突出高度;修整比率β反映了砂轮的锋锐程度,当β稳定时,砂轮达到充分修整。因此修整力反映了砂轮表面形貌和磨削性能,根据修整力的变化可以把握砂轮的修整进程。     

烟气轮机动叶片的参数化建模及加工仿真

运用NURBS曲线拟合算法将节点插入算法应用到动叶片截面型线造型中,采用UG软件中的NURBS样条曲线构造器功能在多个截面上准确绘制出动叶片的截面曲线造型,并利用NURBS曲面造型模块生成烟气轮机动叶片的实体模型。对零件结构特点进行工艺分析,运用UG的加工模块进行加工仿真,生成刀具轨迹并进行试验加工,为后续烟气轮机动叶片的数控加工提供依据。     

利用光固化树脂作为结合剂的超薄型切割砂轮的研制

利用光固化树脂作为结合剂研制成功厚度为０．１５ｍｍ的超薄型金刚石切割砂轮,并完成了对单昌硅片的切割试验。研究结果表明,经ＳｉＯ２微粒增强后的光固化树脂可以替代热固化树脂用作超薄型切割砂轮的结合剂,微粒添加量的大小是影响超薄型切割砂轮的机械性能和切割精度的一个重要因素。     

基于MATLAB与UG的汽轮机叶片造型及数控编程研究

将测量的叶片截面数据经Matlab软件平滑处理,再将平滑处理后的数据导入UG,基于UG软件的强大建模功能和曲面编辑功能,采用NURBS方法建立汽轮机叶片的空间样条曲线,对叶片进行了几何造型;在CAD模型的基础上,进行了叶片的数控加工工艺流程规划,并用软件的CAM功能对叶片进行了数控加工仿真。     

金刚石圆锯片基体及锯齿结构的特性分析(一)——防侧面磨损、防应力变形、改善冷却性能的锯片结构

金刚石圆锯片是金刚石类工具中消耗量最大的刀具 ,优化金刚石圆锯片基体及锯齿结构是改善锯切效果的重要途径。综合介绍了国内外优化金刚石圆锯片基体及锯齿结构的有关成果 ,分析了各种防侧面磨损、防应力变形、改善冷却性能的锯片基体及锯齿结构的特点、生产价值及存在问题     

金刚石砂轮刀片划切过程性能分析与三维建模

介绍了硅片加工过程中3种划片方法及划片机国内外发展趋势.对金刚石砂轮刀片进行力学分析,应用有限元分析软件建立砂轮刀片回转模型,得到刀片的应力图.通过仿真得到:砂轮刀片切向应力总是大于径向应力,切向应力的最大值发生在砂轮刀片孔壁处.并且,应用基于特征的实体造型系统Pro/Engineer,建立了划片机划切过程模拟模型.为进一步进行参数化设计打下基础.     

后掠式叶片气动外形优化设计

后掠式叶片具有载荷自适应性，提出了一种以自然样条曲线为后掠曲线，以扭角为优化参数的后掠式叶片优化设计方法。以直叶片模型为设计起点，通过Profili软件获得叶片的截面数据并计算叶片翼型在不同攻角下的升力系数与阻力系数，以叶片功率系数最大以及叶片根部载荷最小为优化目标，采用遗传算法对叶片进行优化设计。根据优化结果获得的参数，建立后掠式叶片三维模型，在ANSYS Workbench中建立流场模型进行仿真分析得到叶片模型的压力分布情况。结果表明，通过对扭角、后掠值进行优化，后掠叶片模型对比直叶片模型其受到的载荷有所减小，优化设计方法可以用于指导后掠叶片的设计。