球面心轴的加工工艺

球面心轴的加工主要从以下几个方面着手:工艺分析,加工步骤,相关尺寸的计算,车刀及工夹量具的准备,车削圆球,深孔,平面槽,外沟槽应注意的几个问题,零件的加工及测量。     

对辊破碎机球面轴承衬的加工

本文对对辊破碎机球面轴承衬的加工过程进行了全面分析,提出了切实可行的工艺方案。     

大跨度球面网壳结构表面风压间歇特性研究

在同济大学TJ-3风洞试验室对大跨度球面网壳结构进行刚性模型测压试验。通过对结构表面风压信号进行连续及离散小波变换,得到各尺度小波系数时程。对结构表面测点信号的尺度能量比率,间歇能量比率及间歇因子三个参数进行比较性分析,得到以下结论：（1）尺度11处,环向测点尺度能量随位置的变化很小,而在尺度12处侧向测点1－7和1－19的尺度能量明显大于其他区域,约为迎风及背风区域测点1－1和1－13的2倍;（2）测点1－7和1－19的间歇能量主要集中在尺度11处,而测点1－1和1－13的间歇能量在各尺度分布较为均匀;（3）测点1－1,1－7,1－13和1－19的间歇因子随尺度的变化趋势相似,在低尺度区变化平缓而在高尺度区域迅速增大。上述说明,结构表面不同区域的风压信号间歇特性不尽相同,可以进一步为结构风压基本特性的精细化分析提供帮助。     

基于五轴数控加工的球面铣削研究

本文研究了高精度球面加工的方法,阐述五轴加工方案的特点,着重研究五轴机床在球面加工上的相关方法及技术。     

电火花加工工件表面粗糙度的评定与测试

电火花加工的加工表面与切削加工表面有很大的区别。但是,目前电火花加工工件的表面粗糙度仍然沿用切削加工表面粗糙度的评定方法和测试手段,这样不能准确地反映火花加工后工件表面的真实形貌。本文根据电火花加工的特点,提出电火花加工工件表面粗糙度的评定参数和测试方法。     

复合材料的切削加工表面结构与表面粗糙度

普通金属材料的切削加工理论表面粗糙度可以用公式计算。复合材料经切削加工后其表面留有各种凹凸缺陷,这些谷峰轮廓并非由刀刃直接切出,故不宜用现有普通材料的公式计算其理论表面粗糙度。纤维增强复合材料的切削加工表面结构和粗糙度与切削方向密切相关。颗粒增强复合材料无方向性,其已加工表面结构和粗糙度主要受增强颗粒硬度和粒度以及含量控制。增强体与基体的界面强度及切削刀具和工艺条件对复合材料加工表面粗糙度有很大影响。      

钛的镜面加工

日本TDC公司成功开发出表面粗糙度在3nm以下的纯钛超精密镜面加工技术，并开始应用于牙科镜等。该公司是对不锈钢等特殊钢、铜等有色金属、难熔金属、陶瓷、玻璃、树脂等进行镜面加工的公司。能进行表面粗糙度为Inm、平面度为0．1um的超精细镜面加工。但对纯钛进行粗糙度3nm以下的加工在日本还尚属首次。纯钛制的牙科镜是在对内部难见的牙齿照相时用来进行反光的。与目前主要使用的不锈钢牙科镜相比，纯钛牙科镜不易使人过敏，且不易模糊，即使模糊也可马上被消除。因此需求正在逐渐增加。     

深孔滚压加工技术浅谈

阐述滚压加工的作用和机理,并对滚压加工过程中滚压孔表面的缺陷、滚珠与工件孔口相互擦伤、以及薄壁加工时容易遇到的一些问题进行分析,并给出相应的技术措施。     

一个新的车轮表面加工技术

美国铝业锻造车轮公司申请了一项车轮表面处理技术,称之为Dura-Bright工艺,该工艺使维修变得简易。该工艺既非涂覆,也非精整,而是一种专有的表面处理技术。它是用铝渗入表面,发生反应并与车轮成为一体。这个工艺可用于防止脱皮、开裂或生锈。     

基于CAD/CAM的复杂曲面数控三坐标投影加工误差分析

两刀位点间连线与原有刀具轨迹所在平面的夹角α(或曲面上刀位数据的Z坐标增量Δz)对基于CAD/CAM的复杂曲面数控三坐标投影加工误差十分敏感.当用弦长代替弧长时,投影加工两刀位点间直线插补轨迹的法向加工误差Δt是以原有刀具轨迹走刀步长或行距加工曲面时两刀位点间直线插补轨迹的法向加工误差Δy的cos2α(0°<α<90°)倍.若α(或Δz)达到一定值,就会因原有走刀步长或行距的过渡拉伸而产生严重的过切(步长拉伸时)或欠切(行距拉伸时)现象,使被加工曲面出现明显的折面或残留面.应引入控制参数α(或Δz),根据曲面加工精度要求设定限值αmax(或Δzmax),当α>αmax(或Δz>Δzmax)时,进行刀位密化处理,以保证曲面加工精度.     

叶轮零件集成数控编程与数控加工过程仿真

探讨应用于叶轮类零件的集成数控编程与加工过程仿真技术,给出了其功能结构图与流程图,利用商品化软件SURFCAM和VERICUT构建了集成数控编程与加工过程仿真环境,并利用其实现了一个整体叶轮零件的数控编程与加工过程仿真,实际加工结果表明其能够有效解决叶轮类零件的复杂曲面加工问题.     

The Analysis of the Combined Territorial Machining and Contour Line Machining Based on the CAXA Manufacturing Engineer 2004

This paper introduces the rough machining of territorial machining and contour line machining based on the CAXA manufacturing engineer 2004,and gives an analysis of the combined machining of territorial machining and contour line machining. Finally,it proves the superiority of the combined machining by the example of high speed machining of an aluminium alloy lamina part.     

The critical heat transfer characteristics of an insulated or compound sphere considering heat radiation

Critical heat transfer from an insulated or compound sphere happen in ambient air with natural convection. Thus, heat radiation in such a situation must be considered because natural convection has only a small effect. It is found that the critical heat transfer characteristics considering heat radiation are very different from those neglecting heat radiation. The conventional critical heat transfer characteristics neglecting heat radiation only depend on sphere size, external convection heat transfer coefficient, and insulation conductivity. In addition to the above parameters, the critical heat transfer characteristics considering heat radiation are also related to the surface emissivities of the sphere and the insulation, the surrounding temperature, and the internal convection heat transfer coefficient.     

Machining and surface finishing of brittle solids

Ceramic materials are finished primarily by abrasive machining processes such as grinding, lapping, and polishing. In grinding, the abrasives typically are bonded in a grinding wheel and brought into contact with the ceramic surface at relatively high sliding speeds. In lapping and polishing, the ceramic is pressed against a polishing block with the abrasives suspended in between them in the form of a slurry. The material removal process here resembles three-body wear. In all these processes, the mechanical action of the abrasive can be thought of as the repeated application of relatively sharp sliding indenters to the ceramic surface. Under these conditions, a small number of mechanisms dominate the material removal process. These are brittle fracture due to crack systems oriented both parallel (lateral) and perpendicular (radial/median) to the free surface, ductile cutting with the formation of thin ribbon-like chips, and chemically assisted wear in the presence of a reactant that is enhanced by the mechanical action (tribochemical reaction). The relative role of each of these mechanisms in a particular finishing process can be related to the load applied to an abrasive particle, the sliding speed of the particle, and the presence of a chemical reactant. These wear mechanisms also cause damage to the near ceramic surface in the form of microcracking, residual stress, plastic deformation, and surface roughness which together determine the strength and performance of the finished component. A complete understanding of the wear mechanisms leading to material removal would allow for the design of efficient machining processes for producing ceramic surfaces of high quality. The research was supported in part by the National Science Foundation through grants MSS 9057082, Jorn Larsen-Basse, Program Director and DDM 9057916, Bruce Kramer, Program Director.     

采用分区法提高数控三坐标曲线投影加工的精度

零件加工后表面残留高度不均匀的现象一直是数控曲面加工中亟待解决的问题之一．本文分析了数控三坐标曲面加工行距计算公式，得出了曲面数控投影加工行距与曲率半径的关系．结果表明，曲面曲率半径和曲面截面线加工点处斜率参数对基于CAD／CAM的复杂曲面数控三坐标投影加工误差十分敏感，斜率大的区域因原有走刀行距的过度拉伸而产生严重的欠切现象，使被加工曲面出现明显的残留面．针对这一情况，提出了一种刀具轨迹密化的方——分区域投影加工，该方法的特点是对曲面截面线加工点处斜率参数和曲面曲率半径小的区域．减小行距，并进行刀具轨迹编辑，从而使刀具轨迹的刀位达到密化，改善了残留高度的不均匀状况，提高了曲面加工精度．     

组合曲面的空间环切等距加工

加工后零件表面残留高度不均匀的现场一直是曲面加工中亟待解决的问题之一，本文对曲面加工的几种常用刀具轨迹生成方法进行分析的基础上，提出了一种新的轨迹生成方法－空间环切等距加工。该方法的主要特点是：行距在曲面上按弧长保持相等，生成的刀具轨迹切削行分布均匀，可有效地解决曲面零件加工表面残留高度分布不均匀的问题。     

Small amplitude oscillation of a sphere in viscous fluid

Abstract

The Oseenlet and the potential doublet for the oscillatory Oseen's equation are obtained. A new solution based on the singularity method for an oscillating sphere with small amplitude of osicllation in a viscous fluid is presented in this paper by applying these two fundamental solutions.     

低温环境下球面法兰的理论设计

采用球面法兰连接,可以对空间连接位置按照设计角度进行角度补偿,由于球面法兰具有角度补偿特点,在对空间管路布局有严格要求的领域将会得到广泛应用.在球面法兰设计中除要参照常规法兰的设计方法外,还要考虑球面法兰本身所具有的特点,包括槽密封结构的确定,球面半径及位置的确定,补偿角度的设计,因角度补偿而带来的螺栓受力分析等.通过理论分析及尺寸协调,给出了以上内容的设计原则和公式.     

The Research of CNC Machining Cutter Choice Based on CAXA

The article introduces the unique characteristics of CNC machining center cutter compared to traditional cutters,analyzes the choice of CNC machining cutter and factors of choice.Meanwhile,proved by the examples with manufacture software CAXA2004,the correct choice of CNC machining center cutter can give full play to the advantages of CNC machining and improve the economic efficiency and production levels of enterprises.