低黏润滑轴承可靠性强化试验中磁力加载研究

为给核主泵水润滑半尺寸轴承可靠性强化试验提供载荷环境,研究基于水润滑轴承失效模式的强化试验原理,并研制一套轴向和径向磁力加载系统。通过选择磨损、润滑和振动三种典型失效模式并给出对应的试验方案,研究水润滑轴承可靠性强化试验原理,揭示载荷与失效的定性和定量关系,据此提出水润滑半尺寸轴承强化试验的静/动载荷需求。设计并建造磁力加载系统,包括结构和测控两个模块。其中,轴向加载组件的静载与动载结构独立,径向加载组件采用8级式,测控模块支持开环和闭环两种控制策略。设计专项试验验证加载系统的性能。研究结果表明,磨损失效试验算例中比压增加20%时,瓦块磨损量增加1.0~1.2倍,启停次数减少50%~54%;轴向加载组件在间隙2 mm、电流1.2 A时可产生100 k N静载,并可实现脉冲和谐波加载;径向加载组件可实现3.7 k N静载、约500 N幅值脉冲和115 N幅值谐波动载功能。初步验证在水润滑轴承可靠性强化试验中引入电磁加载技术是可行的。针对引入加载装置的多场耦合轴承试验系统,采用人工调节电流的开环加载控制策略更有效。     

静压气体轴承静刚度的动态测试新方法

以环面节流静压气体球轴承为例,建立轴承动静态刚度与气膜位移-动态力频响函数的数学模型;借助数学分析和数值试验,从理论上揭示了轴承气膜位移-动态力频响函数与气膜静刚度、动刚度之间的联系,指出静压气体轴承静刚度的测量可以通过测量低频下气膜频响函数的幅频特性来代替.介绍球轴承气膜幅频特性测试装置的工作原理及测试系统固有模态对测试结果的影响.实测结果表明,静压气体轴承静刚度的动态测试新方法是正确可行的,气膜与承载质量构成的本质非线性二阶振动系统,其低频段的动态刚度数值仍然等于该工作点处的静刚度.新的测试方法,能够实现轴承静态刚度的在线自动测试,提高静刚度的测试精度和效率;将激振频率扩展到机械系统通常涉及的频段后,可以同时得到轴承的动静态刚度和气膜位移-动态力的幅频特性,这对于气体轴承稳定性及精密轴系动态性能的研究具有重要的意义,是轴承的静态测试所无法实现的.     

偏载下大长径比水润滑轴承分布式动特性参数识别方法

为了解决偏载下大长径比水润滑轴承分布式动特性参数识别问题,建立水润滑轴承的两支点分布式动力学模型,提出水润滑轴承分布式动特性参数的识别方法,并验证该动特性识别方法的可靠性。通过仿真试验,引入加载和位移信号扰动对轴承分布式动特性参数识别的精度进行分析,开展偏载水润滑轴承分布式动特动特性试验。结果表明：随着激振力振幅扰动的增加,刚度和阻尼系数的识别误差线性增加;激振力相位扰动对刚度系数的影响较小,对阻尼系数的影响较大;随着位移幅值扰动的增加,刚度和阻尼系数的识别误差增加;位移信号的相位扰动对刚度系数的影响较小,对阻尼系数的影响较大;若要求刚度和阻尼的识别误差小于10%,则激振力和位移信号的扰动幅值应小于10%;若要求刚度和阻尼的识别误差小于20%,则这2个信号的扰动相位扰动偏差应小于1°。     

非接触式电磁加载水润滑轴承监测系统

在水润滑轴承试验研究中,传统机械或液压等接触式加载方式存在振动、噪声、发热与摩擦磨损等问题,另外,监测系统特别是软件功能还不完善,影响轴系稳定运行与测试结果准确性。针对上述问题,设计了非接触式电磁加载装置（电磁加载力大小及角度均可调节）,并基于LabVIEW开发了水润滑轴承监测系统;应用该系统对水润滑橡胶轴承进行水膜压力测试试验,并将试验结果与仿真结果进行对比,结果表明,系统运行稳定,测试数据可靠,实用效果良好。     

高速电主轴动态性能试验

设计了一款集成多种检测功能的高速电主轴试验样机,其内置的温度传感器可测量轴承和定子的温升,编码器可测量转速并实现闭环控制,电涡流传感器可测量转子的三维振动特性和热膨胀量,并可根据实际工况在线调节轴承预紧力。另外,搭建了一套通用性较强的高速电主轴动态性能综合测试系统,基于磁流变液剪切原理和高压水射流冲击原理分别解决了高速电主轴动态扭矩和径/轴向力加载难题,可全面地测量高速电主轴的温升特性、回转特性、输出特性、电磁特性和动态支承刚度,并通过试验验证了磁流变液动态扭矩加载系统、高压水射流径/轴向力加载系统、动态支承刚度测试系统、机械摩擦损耗测量方法和预紧力在线调节装置的有效性。     

水润滑轴承加载装置动态磁热耦合机理研究

针对水润滑轴承动态试验研究中电磁加载装置发热以及电磁力不稳定等现象,为了给轴承研究提供准确载荷,对电磁加载装置动态下的磁热耦合机理进行研究。首先建立了电磁加载装置能量损耗数学模型,对能量损耗进行理论分析;其次,构建了电磁加载装置物理模型,进行磁热耦合仿真分析,得到了磁感应强度、铜损耗以及铁损耗的变化规律;最后,进行电磁加载装置能量损耗试验。研究结果表明：动态下电磁力不稳定的主要原因是加载装置存在能量损耗,且以铜损耗与铁损耗为主;能量损耗与轴转速、加载装置激励电流以及初始温度有关,在激励电流1～3 A、转速0～1 800 r/min以及温度22～50℃工况下,电磁力试验值与仿真值最大误差为4.7%。     

正弦激振测定轴承的刚度和阻尼

在研究机床主轴系统动态性能时,必须知道轴承的支承参数,即,径向刚度K、径向阻尼C_r、角刚度K_c和角阻尼C_a,见图(1)。目前这些参数值,往往是通过试验确定。在结构分析中,刚度值可以通过静态或动态试验来测定,但阻尼系数的识别只能用动态方法测定,所以一般采用动态试验同时测定刚度和阻尼。在被测系统上施以单频的正弦扫频激振或是宽频的瞬态的随机激振,测出系统在激振力F的响应,根据参数识别的基本理论,就可求出系统的各参数。笔者在对某型机床主轴特性进行研究时,为了建立可供电算的主轴系统力学模型,采用一些     

大出力液压激振器

随着现代工程技术的发展,对各种机械产品刚度、振动和噪声的限制日益严格。对样机产品进行准静态及模态分析,掌握产品的动力特性,可以有效地改进产品的设计。要对产品进行准静态和模态分析,必须具备一套激振设备。作为机床及机械构件的激振,由于其刚度范围变化比较大,要求激振力值范围和激振频率范围都比较大。此外,还要求同时提供静态力和动态交变力来激振。计算机技术的突飞猛进的发展,使测试技术、分析技术迈入了一个崭新的阶段。德、美、日等国家相继开发了采用电液伺服技术的电液激振器,开创了动态激振的新时代。我国80年代初,开始将电…     

水润滑轴承加载装置电磁力动态变化机理研究

针对电磁加载装置电磁力在动态载荷模拟试验中的不稳定现象,为了给水力机械中的水润滑轴承性能研究提供准确载荷,电磁力动态变化机理需深入研究.首先,通过理论推导得到了电磁加载装置电磁力动态变化数学模型;其次,建立了电磁加载装置物理模型并进行有限元分析,获得了电磁力、磁阻力矩与磁通密度等参数的变化规律;最后,进行了电磁加载装置...     

球面螺旋槽动静压气体轴承试验台的研制及试验分析

为研究气体轴承的工作机理和静动态特性、设计了球面螺旋槽动静压气体轴承试验台,通过转子升降速试验分析转速-时间、碰磨电压-时间曲线,得到转子的起飞转速为15 762 r/min;通过轴承轨迹、频谱试验研究轴承-转子系统稳定运行到失稳过程的振动变化特性,进一步使用MATLAB,MYSQL数据库及数据处理系统对试验数据进行在线和离线处理,求得气体轴承刚度、阻尼等静动态特性与供气压力、转速的变化关系;通过电磁激振系统对转子进行加载试验,研究刚度、阻尼与激振频率变化关系。试验表明:试验台可测量气体轴承的转子转速、振动位移、轨迹、频谱、起飞转速及刚度、阻尼等静动态特性系数,研究气体轴承稳定运行及失稳过程静动态特性变化和运行参数对轴承静动态特性的影响。     

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.     

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。     

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....     

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.