圆柱族包络面的非等径重构问题的理论研究

在机械设计与制造中 ,常遇到由一圆柱面运动生成的包络面是否能由另一半径不同的圆柱面运动来重新生成的问题 ,即圆柱族包络面的非等径重构问题。本文以等距曲面和包络理论为工具对此问题进行了研究。在得出包络面、轴迹曲面、等效轴迹曲面互为等距曲面的结论的基础上 ,研究了轴迹曲面可展与不可展两种情况下的非等径 (一次 )包络重构问题 ,得到了一些有价值的结论。然后研究并提出了两重包络重构方法。这些结论和方法对指导圆柱族包络面的设计与制造具有重要价值     

圆柱凸轮侧向传动机构圆柱凸轮廓面研究

重点介绍了一种新型无齿减速器,结合图解法与解析法并利用简单的空间几何与运动方法,对无齿减速器的核心传动件圆柱凸轮侧向传动机构廓面进行研究。利用半径为Rj的圆柱面截取凸轮的螺旋面得到圆柱面上螺旋线,求解螺旋线方程。通过对圆柱面半径Rj在一定区间范围内连续取值,利用连续变化螺旋线反求螺旋面方程。再利用该方程通过数学工具Mathematica进行圆柱凸轮螺旋线求解与圆柱凸轮轮廓造型。通过数控机床对样品进行试制从而验证研究的可行性。结果表明：圆柱凸轮廓面计算实际可行,圆柱凸轮侧向连续传动机构传动平稳。     

用端铣刀铣削圆柱面的误差计算

图1所示的工件，其上相距722mm的两个平面相切于R361mm圆柱面，因此，该圆柱面无法按常规方法在车床上车出，因圆柱面长度超出插床的冲程高度，也无法插削；在龙门刨床上用赶刀法成形创出国柱面，劳动强度大，用其它加工方法，都要制造专用工装。经分析后，我厂在落地镗铣床上用硬质合金端铣刀企铣出R361mm图拉面及两相切平面，效果较好．既不需专用工装，又提高了加工效率。如图2，工件装卡在镗铣床的回转工作台8上．加工时，端铁刀盘2旋转作主运动，同时工件由回转工作台带动作旋转送给运动。铣完一刀，切主。个国技带，然后铁刀2向上移…     

刀具空间运动扫掠体包络面建模的双参数球族包络方法

将锥刀、鼓刀和环刀的切削刃回转面表示为单参数可变半径球族的包络面,利用双参数球族包络理论推导出这三种刀具在一般空间运动下的扫掠体包络面的解析表达式,对于环刀还给出两种边界线的计算方法,所提出的原理也适用于其他类型的回转刀具。该方法可用于多轴(包括并联机床)数控加工干涉检验、精度评估、行距优化、路径生成等的全面数字化描述和并行计算处理,锥刀五轴侧铣加工精度校验的结果表明该方法具有很高的精度和稳定性。     

螺旋面的加工方法分析及工程应用

阿基米德螺旋面是机械加工常见的曲面,通过对圆柱面族的包络面方程分析,提出了外径、内外径差、导程都较大的螺旋面加工方法,并用该方法加工了一套螺旋叶片胎具,实践证明该方法切实可行。     

基于斜齿小齿轮的面齿轮的齿面生成研究

文中提出了基于斜齿小齿轮的面齿轮传动的两种几何设计方法,一种是利用传统的螺旋渐开线小齿轮的包络原理,另一种是利用由齿条刀具生成的小齿轮的包络原理;推导了两种情况下面齿轮的齿面方程,并讨论了齿宽的限制条件,实现了面齿轮齿面的可视化.     

常径圆纹面二次包络的特征和应用

应用平行曲面和平行共轭齿面偶的概念揭示了常径圆纹面二次包络的特征并且系统地研究了尼曼蜗杆传动和圆柱面二次包络弧面蜗杆传动这两个实例,获得了一些新的结果。     

多头平面双包络环面蜗杆副的研制与测试

一、概述平面双包络环面蜗杆传动是一种新型的蜗杆传动。蜗杆齿面是空间曲线密切面的包络面,它是以一平面为母面,按一定的相对运动规律包络而成的。蜗轮齿面则以上述平面包络蜗杆齿面为母面,通过另一次包络运动形成的包络曲面,它是由理论上与该蜗杆一致的或近似的滚刀展成的。形成这一传动副,需要两次包络运动,所以称之“平面二次包络环面蜗杆传动”。     

复合铣削轨迹对表面质量的影响

复合铣削一般由多个旋转运动和多个移动复合而成。通过齐次变换矩阵法得到了复合铣削轨迹方程和复合铣削轨迹，探究了复合铣削轨迹对表面质量的影响，结果表明：复合铣削的包络面的表面粗糙度明显低于未包络面，复合铣削的未包络面与普通端铣的表面粗糙度相差不大；进给量对复合铣削的未包络面的表面粗糙度影响不大，而包络面的表面粗糙度随进给量增大而增大；未包络面和包络面的表面粗糙度Ra均随着切削速率比k的增大而减小；复合铣削的残余应力比普通端铣的残余应力小，而复合铣削中的包络面的残余应力比未包络面的小。     

斜齿面齿轮蜗杆砂轮磨削的双参数法

针对面齿轮硬齿面磨削加工中存在的困难,提出用蜗杆砂轮磨削的双参数法来磨削面齿轮。借助一个渐开线斜齿圆柱齿轮的刀具齿面推导出蜗杆砂轮齿面,由蜗杆砂轮齿面经双参数包络生成斜齿面齿轮齿面。确定了刀具轴与蜗杆砂轮轴夹角大小,分析了双参数包络的形成及包络过程,并用计算机形成了可视化结果,获得了理想的面齿轮齿面。     

An Examination of Thermionic Emission Due to Frictionally Generated Temperatures

The emission of electrons from a surface due to heating-referred to as thermionic emission-is examined theoretically for sliding contact. High local temperatures generated by friction at the contacts between rubbing surfaces can activate the emission of electrons and influence tribochemical reactions. A thermal model previously developed by Vick and Furey [1,2] for sliding contact is used to predict the temperature rise over the surface. This predicted temperature rise, along with the bulk temperature of the material, is used in the Richardson--Dushman equation for thermionic emission to predict the current density from the surface. The total current discharged from the surface is obtained from an integration of the current density. Results demonstrate that high local temperatures generated by friction at the contacts between rubbing surfaces can activate the emission of electrons, with local spikes in the current density occurring in the vicinity of the peak temperature. In addition, relatively large changes in both current density and total current result from relatively small changes in either material properties or sliding conditions, such as velocity or applied load. Since the true area of contact is likely to evolve in a highly dynamic fashion, a study using time varying, multiple contacts was also conducted. Results suggest that the locations of high local temperatures and thermionic activity are likely to be short lived and random.     

The Isothermal Lubrication of Cylinders

When the hydrodynamic problem of cylinder lubrication is considered, two distinct types of solution emerge. For light loads the cylinders retain their unloaded geometry; the Martin solution for this condition is well known. When the contact forces are large, significant elastic deformation may occur; the resulting elastohydrodynamic regime has been extensively analyzed in recent years.

Equations are now available for the calculation of minimum film thickness in the “rigid” and “elastic” situations. In this paper computing methods appropriate to each range of conditions are summarized, and the nature of the solutions is considered in some detail. In particular the valid range of application of the “rigid” and “elastic” film thickness relationships is discussed. An intermediate range of conditions between the “rigid” and “elastic” regimes is defined.

Finally, a chart is presented to enable a particular problem to be located in the “rigid,” “intermediate,” or “elastic” zones.     

Optimal Upsetting of Composite Cylinders

Russian Engineering Research - The upsetting of a composite cylinder in frictionless creep is analyzed in energy terms. Three loading programs that lead to upsetting of the cylinder by the same...     

发动机排放物生成的原因分析与控制技术

通过对发动机排放物产生的原因进行分析,了解排放物的组成和分布情况,系统地阐述了控制排放物产生的技术和方法,从而抑制和减少排放物对大气环境的污染。     

Surface Temperatures Generated by Friction with Ceramic Materials

For tribological applications of ceramics, surface temperatures and thermal effects produced in frictional processes are important not only in influencing possible mechanisms of friction, wear, and lubricant film failure but also in initiating protective film formation, e.g., as in tribopolymerization. As part of a continuing combined experimental and theoretical study of surface temperatures generated by friction, the fundamental Greens function approach has been applied to a number of ceramics including those used in tribological applications such as bearings and advanced low heat-rejection ceramic engines. The ceramics examined consisted of (a) alumina, Al₂O₃, (b) single crystal sapphire, Al₂O₃, (c) partially stabilized zirconia, ZrO₂, (d) tungsten carbide, WC, (e) silicon carbide, SiC, and (f) silicon nitride, Si₃N₄. In addition, three forms each of silicon carbide and silicon nitride were included in this study, i.e., sintered, hot-pressed, and reaction-bonded.

Assuming a single area of real contact, calculated ratios of average surface temperature rise to coefficient of friction plotted against area of contact, velocity, and load on a logarithmic scale are presented for all the above ceramics for A-on-A (self-mating) contact as well as an example of a ceramic in sliding contact against steel. The results show that as expected, very high surface temperatures can be generated by some ceramics, particularly those having very low thermal conductivity (e.g., zirconia), high hardness, or a combination of both. However, not all ceramic combinations produce high temperatures. It is suggested that the information developed may be useful in understanding the wear behavior of ceramics as well as in designing novel anti-wear approaches for ceramic lubrication.     

电解水制氢气微机监控系统

采用工业控制计算机,对电解水制氢生产工艺的各种参数进行自动监测.并根据电解液电导率与温度及压力等因素的变化关系,采用PI控制算法,自动调节整流器的电流,保证了氢气的产气量和系统的可靠运行.     

高压柱形气瓶振动特性分析

针对车载高压柱形气瓶振动问题,运用板壳振动理论对其进行振动特性的计算分析,获得此类气瓶各阶振动频率及振型.同时,运用ANSYS 12.0进行仿真计算,得到该气瓶的相应振动频率和振型.比较分析两种方法所得振动频率的异同和各自振型的变化特点,为该类气瓶在振动环境下使用的安全性能分析提供支撑.     

复合工艺制备的表面微凹坑织构的摩擦性能研究

在构建的激光电化学复合微加工系统上,采用皮秒脉冲激光辐照与电解刻蚀复合加工方法在7075铝合金表面制备出不同尺寸的阵列凹坑微织构。采用共聚焦显微镜观测复合加工织构试样表面形貌,采用MFT-5000型RTEC摩擦磨损试验机研究润滑条件下凹坑织构的摩擦学性能,并探讨直径、深度、面积密度对减摩性能的影响。结果表明:复合加工工艺制备的表面微织构具有良好的表面形貌;润滑条件下材料表面的凹坑型织构能显著改善其摩擦学性能,相比光滑表面最高可降低摩擦因数30%;在实验参数范围内,凹坑的直径与面积密度对材料表面摩擦性能影响较大,凹坑深度对摩擦性能影响较小。     

连杆机构创成轨迹测量方法的理论探索

研究的对象是四杆机构的创成轨迹 ,拟以激光作为信号源 ,以 CCD(或照相机 )为激光信号接受器 ,测量连杆中点在运动过程中形成的轨迹。本文提出以凹透镜散射法将待测光源转化为镜头可以直接捕捉的理想光源 ,从而大大提高了点的测量精度 ,充分利用了激光作为信号源所体现的优势。本文还提出了测量过程中的位置参数优化的方法和公式。