基于有限元的三轴测试转台静动态特性研究

通过几组实验发现测转台轴系的回转精度在电机(包括其它附件等)和负载安装前后的值相差很大,由此认为框架的变形对测试转台的回转精度有着较大的影响.采用有限元分析方法,对三轴转台轴系的动静态特性进行了研究,建立了轴系的有限元模型,应用有限元分析软件ANSYS10.0对模型进行了分析,得出框架的静态变形、框架的各阶固有频率及其振型,并对结果进行了模态分析.     

超小型机载稳定平台轴系精度分析

超小型机载稳定平台的轴系精度在很大程度上决定着设备的定位精度。为了提高设备的定位精度,需要对平台的轴系精度进行严格地控制。这要求设计轴系时,在现有加工水平和轴承精度的基础上,充分保证轴系具有高的回转精度。以俯仰轴系径向回转精度为例,分析了轴系径向回转精度的结构因素,并按照标准不确定度B类评定方法,对其结构参数的标准不确定度进行了计算,可得俯仰轴系径向回转轴线的扩展不确定度为0.014mm,满足编码器安装对轴系的精度要求。通过20台套超小型机载稳定平台轴系径向跳动检测数据,对轴系精度不确定度评定的结果进行了验证。数据与评定的结果一致,满足编码器安装精度±0.015mm的指标。结果表明对轴系精度的分析和对其结构的设计合理。     

精密转台轴系设计分析与验证

针对由于测角传感器的精度不断提高,转台的回转精度和稳定性成为制约系统精度的主要因素问题,对转台轴系设计进行了深入分析研究。完成了一维精密转台的轴系结构设计,并对其进行了有限元分析。在此基础上,通过静力学分析,研究了主要零部件对轴系回转精度的影响情况;通过动力学分析,研究了轴系的固有频率及其振型。搭建了转台测角精度测试平台,采用了自准直仪结合多面棱体获取角度测量误差,并进行谐波误差补偿。研究结果表明,最终转台的角度精度达到±1.5″,证明该转台设计是可行的。     

多光栅测角系统精密转台轴系设计

精密转台是精密测量仪器的重要组成部分,转台轴系精度对仪器整体精度有重要影响。文中根据多光栅测角传感器特点,设计了一台一维精密转台,通过有限元分析完成转台的力学性能分析。其中,使用ANSYS软件对转台进行静力学分析,仿真使用环境下转台的应力分布和位移分布情况;通过动力学模态分析,得出转台各阶振型及相应固有频率。完成设计和仿真后,使用千分表对转台轴系的轴向跳动和径向跳动进行测量,通过建立数学模型分析转台回转精度,验证转台轴系回转精度达到4. 3″。     

数控轧辊磨床头架可回转主轴的设计

介绍了一台数控轧辊磨床的头架可回转主轴轴系的设计过程.重点分析了轴承的选择、支承跨距的合理布置、滚动轴承的消隙和轴承的润滑方式.根据数控轧辊磨床的特点,对主轴系统进行了结构设计.通过对数控轧辊磨床头架可回转主轴的有限元分析,优化了主轴系统.数控轧辊磨床的头架可回转主轴轴系的设计成功,对提高磨床头架主轴的回转精度、承载能...     

切入磨削时砂轮圆弧修整对沟道精度的影响

在刃磨圆弧砂轮时,一方面砂轮中心平面应通过金刚石笔头回转线,否则影响沟道的轴向位置精度;另一方面金刚石笔头摆动平面应通过砂轮轴线,否则影响沟道的几何形状;通过分析得出,内圈沟道磨削时应尽可能选用大直径的砂轮;对于外圈沟道来说,尽可能减小金刚石笔的回转偏角,以抑制沟道误差的增大。附图４ 幅,表１个,参考文献２ 篇。     

提高轴系精度的谐波干涉研磨法

一、问题的提出 轴系是构成精密计量仪器和精密机床的核心部件。轴系的回转精度也是影响测量精度和加工精度的关键因素。理想的回转精度应该是轴的旋转中心和孔的理想回转中心相重合,并在运动状态下不发生偏离。当然理想的状态是不可能完全实现的。但是随着科学技术的发展,对轴系的回转精度的要求越来越高。不但超出了现代加工设备和技术条     

高精度金刚石工具磨床主轴结构设计及有限元分析

对高精度金刚石工具磨床主轴系统进行了结构设计,分析了轴承预紧力对主轴温升和刚度的影响。分析结果表明轴承预紧力对主轴支承刚度有显著影响。在考虑轴承径向刚度和轴向刚度的基础上,研究并建立了主轴的有限元模型。利用有限元软件ANSYS对主轴单元进行了动静态特性分析,结果表明所设计的主轴系统能够满足金刚石刀具刃磨要求。     

转台密珠轴承应力及过盈量的分析计算

以弹性接触理论中的塑性变形问题为基础,根据密珠轴承轴系的回转精度要求和静负荷能力,推导出最大接触应力和过盈量的计算表达式,在此基础上给出考虑温差和表面粗糙度影响时的修正值,最后,通过实例计算分析过盈量对旋转精度的影响。     

回转精度测评的运动几何学原理与不变量方法

提出轴系回转精度测评的误差运动几何学原理,由转子误差运动、被测几何要素、传感器测试参数等三要素构造轴系回转精度测量的运动几何学模型,建立测量闭环矢量基本方程;推导出轴系误差运动参数测量的完备性条件,讨论回转误差运动参数测量的完备性及其演变形式,阐明各类回转精度测量数据与评价指标的运动几何学内涵。给出轴系回转误差运动的不变量定理,得到轴系回转误差运动的最小球面像曲线与最小准线,从而将轴系回转误差运动分解为角摆误差运动与平移误差运动,建立角摆误差运动不变量、平移误差运动不变量与各类回转精度指标之间的关系,形成轴系回转精度评价的不变量方法,有效地避免被测几何要素不同对测评结果的影响,为轴系回转精度的测量与评价提供理论依据。     

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...     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

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.     

ANGULAR DISTORTION ALLOWABLE VALUE AND ASSESS METHOD OF WELD ON COKE TOWER

A graph as the new engineering method for estimate the safety of bulging deformation of coke tower is proposed. Through stresses analysis of circumferential weld of coke tower and comparing the stresses produced by pressure with heat stress of steady state, residual stress, bending stress produced by both itself weight and wind loads, it showed that the stresses produced by pressure on the angle distortion are the main factor of equivalent stress of the combined stress. After comparing four kinds of stress controlling conditions, the relation to stress with depth of angular distortion, grade of curvature of angular distortion and half of region of angular distortion has been inferred. Graph of deformation allowable value of coke tower for different condition by angular distortion and half of region of angular distortion has been plotted. The five steps for its engineering use have been explained. The lighter the grade of curvature is, the larger of bulge allowance, may be, and the bigger of depth of angular distortion may pose too. For the coke tower with a popular structure of Dg 5 400 mm×28 mm, the result by graph is nearly more than the result of two formulas formed by other research, the error is less than 7.0%. But, the graph can be easily applied to different size of angular distortion.