机匣类零件数控磨抛加工技术研究

该文通过对数控磨抛加工技术的探索与试验,梳理出不同类型的磨抛特征,得到可用于机匣类零件数控磨抛加工的专用刀具及技术方法,根据不同的磨抛特征选用相适用的磨抛工具,并通过调整加工参数、走刀次数及磨抛过盈量得到不同的下屑量及表面质量,实现特殊位置飞边毛刺的数控去除,有效降低了打磨钳工的工作量,提高了磨抛加工的质量稳定性,为自动化加工进行了技术储备。     

机器人磨抛工艺参数优化方法研究

为了确保加工质量和加工效率的最优参数组合,进行了机器人砂带磨抛去除参数的优化方法研究.在分析砂带磨抛过程后建立了表面粗糙度和磨抛去除率模型.运用deform软件对工件磨抛过程进行模拟仿真,建立了磨抛去除率和粗糙度回归方程.以加工表面粗糙度和材料磨抛去除率作为目标函数进行双目标优化,并运用NSGA-Ⅱ算法确定了最优参数组合.以仿真数据为基础进行正交试验,对理论和仿真的结果进行了验证.结果表明,采用所确定的最优参数组合进行磨抛加工试验,能够达到预期的磨抛去除率和表面粗糙度要求,表面加工质量良好,所用工艺参数优化方法可行.     

复杂非球面镜高效超精密车削加工法(英文)

本文中对复杂面形的非球面镜进行了分类,并从加工方法和加工路径优化设计等方面研究了复杂非球面镜的超精密车削方法.对回转对称的复杂非球面镜进行了加工实验,并借助超精密测量技术对各段曲面进行面形测量,依据测量结果实现面形补偿加工.最终粗糙度Ra达5.14 nm,形状精度P-V值达200 nm.采用提出的方法对非回转对称的非球面阵列进行加工路径设计,根据具体面形进行加工参数选择和实际加工,得到粗糙度Ra为7.81nm的表面.实验结果证明了提出的加工方法高效实用,可以满足大部分复杂非球面的应用需求.     

磁流变抛光驻留时间算法

针对磁流变抛光去除量与驻留时间呈线性关系特点,本文以Preston方程为依据,根据磁流变抛光专用机床的运动形式,提出了基于矩阵的磁流变抛光驻留时间算法,该算法通过调整各点驻留时间控制光学器件表面的去除量,达到面形误差修正的目的,适用于非球面等可用通用光学方程表示的回转对称曲面.仿真实验结果表明,采用该算法仿真加工可以使球形表面面形误差收敛至十几个纳米.通过对K9光学玻璃球面进行的磁流变抛光实验,获得了表面粗糙度Ra0.636 nm的球形表面,面形精度P-V值由抛光前的158.219nm减小到52.14 nm,验证了驻留时间算法的合理性.     

一种新的气囊式抛光方法的研究

针对气囊式小磨头抛光方法的缺陷,提出了一种新的气囊式抛光方法。本文对该气囊式抛光法的原理和抛光气囊的结构、运动方式等进行了阐述。在此基础上,结合装置开展了实验,给出了去除量、压力、粗糙度与时间的关系。研究结果表明,利用该气囊式抛光方法对非球面光学零件进行抛光,效果良好,表面粗糙度可达2nm,该方法能满足中高等精度的加工要求;该方法适合平面、球面、非球面、甚至任意曲面的抛光。     

大型非球面主镜能动磨盘加工模型

大型非球面主镜能动磨盘加工（CCAL）是有别于传统加工和数控加工（CCOS）的新型加工工艺。通过对能动磨盘结构的研究,建立了工件的能动磨盘磨削模型,分析了加工中的边缘效应,并采用压强补偿的方法对磨削模型进行了优化。在Φ1300mm（F／2）非球面主镜能动磨盘加工实验中,以该优化的模型仿真的主镜加工面形与经Hartmann-Shack传感仪检测的实际面形基本吻合。     

轴对称非球面镜超精密加工新方法的几何模型

介绍了轴对称光学非球面镜超精密加工的新方法．超精密金刚石切削加工机床的刀具进给机构通常由直线导轨实现．由于旋转轴与同等精度的直线导轨相比，具有制造难度小、成本低及结构紧凑等优点，所以采用具有快速伺服机构的金刚石刀架摆臂代替直线导轨进给运动方式．根据非球面方程，快速伺服机构的微进给量根据车刀摆角实时计算．快速伺服机构、工件以及金刚石刀具的同时运动，可以实现轴对称非球面的超精密加工．构建了回转进给工具路径、快速伺服机构运动以及相关的几何模型．通过计算机模拟验证了该加工方法的简便与可靠性，可以降低非球面反射镜加工的设备投入，提高生产效率．     

DHM-500超精密数控非球面透镜磨床的研制

为了解决非球面透镜加工方法周期长、成本高等问题 ,该文介绍了作者在DHM 5 0 0超精密数控非球面透镜磨床研制中的一些关键技术 ,对其主要结构进行了分析 .该磨床主要用于解决大尺寸非球面透镜的高精度高效率加工问题 .工件主轴、砂轮主轴、转台及溜板全部采用液体静压结构 ,能实现X、Z、B三轴联动的磨削加工 .主轴回转精度为 0 .1μm ;砂轮轴回转精度为 0 .1μm ;转台回转精度为 0 .1μm ;导轨直线度为 0 .5 μm/2 80mm ;系统分辨率为 0 .1μm ;X轴定位精度为± 0 .5 μm /2 80mm ;Z轴定位精度为± 0 .5 μm /170mm ;转台定位精度为± 3″     

航空精密小叶轮数控加工技术

航空精密小叶轮的零件结构特殊,尺寸规格小,叶片极薄,叶片间空间小,圆角小,精度要求高,加工中极易出现断刀、尺寸超差、光度超差等问题,加工难度大,已成为实际生产中的瓶颈。主要针对这种精密小叶轮零件的机械加工部分,确定工艺方案,充分利用数控设备,确定合理的走刀路线,运用UG建模,后置处理生成加工程序,反复调试、试切,优化数控程序,最终实现精密小叶轮的数控加工,并且该数控加工技术可以推广到其它十余种同类零件的加工中,具有一定的工程实用价值。     

使用计算机控制的抛光机加工光学元件

计算机控制的抛光机(CCP)带有一个小的磨—抛工具装置,此装置在计算机的控制下在工件表面上移动。使用这种机器已成功地加工了许多很难加工的基底的光学元件,如铍反射镜、非旋转对称校正板和易变形的非球面反射镜。这些成果表明,计计算机控制的抛光机(CCP)可在很难加工的基底上加工出1/15波的表面。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...     

Effect of Oxide Assisted Metal Nanoparticles on Microstructure and Morphology of Gallium oxide Nanowires

Several researches have been reported about the characteristic of β-Ga2O3 nanowires which was synthesized on nickel oxide particle. But indeed, recent researches about synthesis of β-Ga2O3 nanowires on oxide-assisted transition metal are limited to nickel or cobalt oxide catalyst. In this work, Gallium oxide (β-Ga2O3 ) nanowires were synthesized by a simple thermal evaporation method from gallium powder in the range of 700 - 1000℃ using the iron, nickel, copper, cobalt and zinc oxide as a catalyst, respectively. The β-Ga2O3 nanowires with single crystalline without defects were successfully synthesized at the reaction temperature of 850, 900 and 950℃ in all the catalysts. But optimum experimental condition in synthesis of nanowires varied with the kind of catalyst. As increasing synthesis temperature,the morphology of gallium oxide nanowires changed from nanowires to nanorods, and its diameter increased. From these results, we could be proposed that the growth mechanism of β-Ga2O3 nanowires was changed with synthesis temperature of nanowires. Microstructure and morphology of Synthesized nanowire was characterized by HR-TEM, FE-SEM, EDX and XRD.     

The Influence of Nitrogen and Boron Implant into Silicon Substrate on the Phase and Internal Stress of c-BN Films

Cubic boron nitride(c-BN) film was deposited on a Si (100) substrate by the RF-magnetron sputtering.The mainly problems for fabrication of c-BN films are the low purity and high intrinsic compressive stress. In order to solve the two problems, the c-BN film with the buffer interlayer was deposited on the substrate which had been implanted with nitrogen and/or boron ions. The results show: the implantation of nitrogen ions can obviously increase c-BN content and reduce the internal stress slightly; while the implantation of boron shows no obvious improvement to the content of c-BN, which can reduce the internal stress in the film obviously. In addition, it is suggested that the implantation of nitrogen and boron shows the best result, which not only can increase the content of c-BN, but also reduce the internal stress in the c-BN film obviously.