直纹面叶轮插铣加工关键技术

为提高整体叶轮的粗加工效率,弥补目前商用计算机辅助制造软件在五坐标插铣加工能力方面的不足,研究了直纹面叶轮五坐标插铣加工的关键技术。根据直纹面叶片的偏移边界矢量,利用四元数插值方法计算插铣加工的刀轴矢量,提出并推导了五坐标插铣加工的行距和步距计算公式,保证了插铣加工的材料去除率和加工效率。依据上述算法自主开发了整体叶轮五坐标插铣加工专用计算机辅助制造软件,并对该软件生成的刀具轨迹进行了仿真和实际加工验证。结果证明,该方法在一定程度上提高了叶轮零件的粗加工效率。     

基于FLUENT的叶轮机械内部流场的模拟研究

介绍了FLUENT软件的主要特点及其在叶轮机械领域的应用情况,并且以某轴流风机为例,用该软件进行数值模拟,分析其内部流场变化情况.通过这种模拟,能真实反映叶轮机械内部的复杂流动,为叶轮机械的设计和改进提供理论依据.     

基于UG的叶轮5轴数控铣削编程与加工

叶轮零件结构复杂,其数控加工技术普遍存在编程复杂,困难且效率低下等问题.介绍使用典型的CAD/CAM软件UG7新增的叶轮加工模块,对深窄槽道、大扭角的滑轮发动机叶轮的五坐标加工程序刀路进行编制,大大提高了叶轮加工编程的速度和效率,为叶轮零件的编程加工提供了新思路和方法.     

基于加工特征分类的整体叶轮加工工艺研究

根据叶轮加工专业软件中NC程序模块分类思路以及通用叶轮数控工艺的需求分析,提出了基于加工特征分类的整体叶轮五轴数控铣削程序模块划分方法.在对某型叶轮进行五轴加工工艺编排过程中对此方法进行了工程试用,最后通过VIRICUT加工仿真平台验证了叶轮工艺及特征分类方法的可行性和正确性.     

轴流式叶轮机械试验演示与流场计算显示的混合编程

使用Visual Basic开发了轴流式叶轮机械试验演示与流场计算软件,该软件可对轴流式叶轮机械试验数据进行动态演示,并具有进行多级轴流压缩机S1流面流场计算、实时显示计算迭代过程及对计算结果进行图形后处理的功能.探讨了Visual Basic和Fortran混合语言编程技术.阐述了在Visual Basic中对图形处理软件Tecplot操控的具体实现方法.通过对一台小型轴流通风机的试验验证了该软件的实用性,具有较好的工程应用前景.     

叶轮动模零件的三维建模与数控仿真加工

对叶轮动模零件进行了工艺性分析,采用CAXA2011制造工程师软件完成叶轮动模零件的三维建模;用CAXA制造工程师软件的CAM功能模拟加工刀具轨迹和零件的加工过程,根据数控仿真加工结果编制叶轮动模的数控加工工序卡,用于指导现实加工.结果表明,叶轮动模的加工方法和铣削参数选用合理,对实际生产加工有一定的参考价值.     

离心式三元叶轮焊接坡口五轴加工刀位算法

根据三元叶轮焊接坡口大多采用手工修磨方法加工的现状和某企业对焊接坡口加工的图纸要求,首先将叶片中性面盖盘曲线拟合为NURBS曲线,并对其进行离散处理.再根据切削平面内圆柱铣刀与坡口的几何关系,开发出圆柱铣刀五轴侧铣加工三元叶轮焊接坡口的刀位算法.经仿真与试切加工,完全满足图纸要求.本算法不仅适用于两件焊式三元叶轮,同时适用于手把焊式二元叶轮和开槽焊式二元叶轮焊接坡口的五轴侧铣数控编程.实现了叶轮类零部件焊接坡口的数控加工,可有效的提高叶轮的加工精度和加工效率,提升焊接后叶轮的强度,并极大的减轻了操作工人的负担.     

离心压缩机闭式叶轮电解加工方法的研究

以离心式压缩机闭式叶轮为例,采用电解加工方法加工整体叶轮.介绍了电解加工闭式叶轮的思想,电解加工系统设计,阴极(刀具)的设计及制作方法.并结合实际加工工艺,对电解加工所造成的误差进行了说明,给电解加工在工业上的应用打下了更坚实的基础.     

不锈钢叶轮五轴联动数控加工中仿真技术应用研究

分析了五轴联动数控中心加工不锈钢叶轮的技术难点,并运用仿真技术加以解决.提出了仿真方法和仿真流程,并基于VERICUT仿真平台,以某型号叶轮的加工过程为例,实际进行了仿真.仿真结果显示加工刀具、加工参数对叶轮质量有重要影响.分析了仿真出现的问题,通过改变刀具、优化加工方案,最终完成了加工.实践证明,仿真技术有利于提高不锈钢叶轮的加工成功率,改进加工质量.     

精密小型叶轮的多轴加工技术研究

精密小型叶轮由于加工精度要求高,叶片厚度薄且间距小,一直是叶轮加工的难点.以某小型叶轮为研究对象,用SmartCNC500精雕五轴联动加工中心、红外测头等设备进行加工实验,研究精密小型叶轮叶片加工的技术难点;并用JDSoft SurfMill软件辅助,进行刀具路径的编辑与仿真.通过加工实验,对比一般尺寸叶轮后,得出精密小型叶轮加工的切削参数、刀具路径的调整方法等.通过高端精密设备加工完成高精度的复杂零件,为行业提供了新思路新方案.     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

Limits of topographic measurement by the scanning tunnelling and atomic force microscopes

Parameters describing the topographic character of a surface (height, surface wavelength, slope and curvature) can be derived from equivalent sinusoidal profiles. The response of a surface-measuring instrument may be modelled in terms of instrument parameters such as stylus radius, and scanning range and resolution. The performance of the instrument may then be mapped as a zone in amplitude-wavelength (AW) space to show the sinusoidal profiles it is capable of measuring. In a first-order analysis the STM and AFM are considered as equivalent to contact-stylus instruments with a notional stylus radius equal to the tip radius plus the gap. Comparisons between different instruments and types of instrument are readily made by mapping in AW space. The error arising from convolution of the sinusoidal profile with that of the finite tip may be quantified and plotted as contours in AW space.     

Fractional order nonsingular terminal sliding mode control for flexible spacecraft attitude tracking

This paper investigates a fractional terminal sliding mode control for flexible spacecraft attitude tracking in the presence of inertia uncertainties and extern...     

奥氏体不锈钢表面双辉等离子渗锆的动力学

利用双辉等离子渗金属技术在0Cr18Ni9Ti奥氏体不锈钢表面制备了一层均匀、致密、呈良好冶金结合的渗锆合金层,并对1 060℃下的渗锆动力学进行了研究。结果表明:随着距锆合金层表面距离的增加,锆元素的含量呈梯度递减,扩散系数逐渐减小,而扩散激活能逐步增大;在1 060℃采用双辉等离子技术渗锆时,渗锆合金层表层的空位密度为2.945×(1012~1013)cm-2,与相同温度下采用常规渗金属工艺相比,提高了1~2个数量级。     

气化炉三维扫描测量与数据处理

以德士古气化炉耐火砖的内壁蚀损检测设备为基础,对采集到的点云数据做了进一步处理.通过对数据的筛选和剔除,实现了数据点的平滑降噪细化和精简.然后利用点云对整、网格划分和分色显示等方法,最终完成了内壁腐蚀情况的三维建模.重点讨论了点云数据的预处理及后处理的方法,并根据内壁耐火砖的腐蚀阈值,提出了一种气化炉内壁腐蚀区域的识别与分割方法.对耐火砖的腐蚀分析、气化炉的生产与维修提供了可靠依据,并在工程应用中获得了一致认可.