4种成分车轮钢与U71Mn钢轨钢间的磨损行为

在轮轨磨损试验机上研究了热轧U71Mn钢轨钢和4种成分车轮钢间的摩擦磨损行为,分析了车轮钢化学成分、硬度对磨损行为及磨损机制的影响。结果表明:随着碳元素含量的提高,车轮钢显微组织中先共析铁素体含量显著减少,珠光体晶粒尺寸增大,珠光体中的渗碳体片层变厚,车轮钢的硬度也逐渐增大;随着车轮钢硬度的增大,车轮钢磨损量减少,其主要磨损机制由磨粒磨损和浅层剥层磨损向深层剥层磨损转变,钢轨钢磨损量增加,其主要磨损机制为浅层剥层磨损。     

车轮材料对轮轨系统匹配性能的影响

利用MMS-2A型微机控制摩擦磨损试验机研究4种含碳量不同的车轮材料分别与PD3热轧钢轨进行匹配的磨损与疲劳性能。结果表明：随着车轮材料的含碳量增加,硬度增大、耐磨性增强,导致磨损量降低,轮轨系统的磨损量呈现先减小后增大的趋势;车轮试样的塑性变形层厚度随含碳量的增加而减小,抗疲劳性能加强;车轮试样表面由严重剥落损伤向轻微剥落转变,伴随有一定的黏着磨损;钢轨试样表面以剥落磨损为主。     

不同轴重下轮轨损伤特性试验研究

利用MMS-2A型微机控制摩擦磨损试验机研究了不同轴重下轮轨摩擦磨损性能。结果表明:随着轴重的增加,轮轨间的摩擦系数呈增大趋势,且轴重越大,摩擦系数趋于稳定后的波动系数越小,车轮和钢轨的磨损加剧,但轮轨材料硬度值的差异会导致磨损量的增幅差异;轮轨间接触应力的增加,会导致晶体滑移线向材料里层滑移深度增加,塑性变形层加厚;随着轴重的增加,车轮材料的磨损机制由黏着磨损逐渐向疲劳裂纹方向转变,钢轨材料主要变现为疲劳磨损,由疲劳短裂纹向疲劳长裂纹及多层剥落磨损转变。     

不同轮轨材料硬度匹配行为及其机制的初步研究

合理的轮轨材料硬度匹配能够显著提高列车的运行安全,为探究不同轮轨材料的硬度匹配行为及机制,利用MMS-2A摩擦磨损试验机对不同轮轨材料进行相应的匹配试验。结果表明:低轴质量下随着轮轨材料硬度比的升高,轮轨间主要磨损机制由磨粒磨损向疲劳磨损和氧化磨损过渡,轮轨材料整体的耐磨性显著提高;高轴质量下轮轨接触应力显著增大,轮轨硬度比的增大能够显著地减轻轮轨材料间的磨粒磨损,轮轨材料整体的耐磨性显著提高。因此,在现有轮轨接触条件下适当增大车轮硬度,使车轮硬度接近钢轨硬度能够显著改善轮轨材料磨损状态,而且对于重载工况效果更为明显。     

新型CL60钢地铁车轮摩擦磨损试验研究

为了提高地铁车轮的服役性能,对车轮用CL60钢材料中Si、Mn、Cr等元素的质量分数进行重新设计和优化,研发新型CL60钢地铁车轮,通过GPM-60摩擦磨损试验机模拟轮轨磨损试验,研究原CL60钢车轮与新型CL60钢车轮在实验室条件下的磨损特性。基于赫兹模拟准则设计计算了模拟试验采用的轮轨试样尺寸、施加的载荷和转速;通过不同载荷工况下的摩擦磨损试验和轮轨材料微观组织分析,研究2种轮-轨试样的磨损量、磨损率、塑性变形及表面形貌的变化规律及特征,对新型CL60钢车轮的使用性能进行评价。结果表明：与原CL60钢车轮相比,在不同载荷下新型CL60钢车轮试样磨损量、轮-轨试样总磨损量、磨损率及摩擦表面塑性变形层厚度均大大降低,其抗磨损性能和塑性变形能力得到了改善。     

轮轨材料匹配摩擦学试验研究

根据赫兹接触理论,使用MMS-2A微机控制摩擦磨损试验机对3种含碳量不同的车轮材料分别与U71Mn热轧钢轨进行匹配试验,研究其磨损与接触疲劳性能并进行微观形貌分析.结果表明:车轮钢材料的耐磨性与硬度成正比;随着轮轨材料硬度比增大,磨损机制由黏粘着和疲劳磨损转变为磨粒磨损.     

中等强度沙尘暴环境下钢轨硬度对轮轨滚动磨损与损伤影响

为研究戈壁和沙漠中等强度沙尘暴环境下钢轨硬度对轮轨滚动磨损和损伤的影响，采用风沙环境双盘滚动接触疲劳试验机对四种不同硬度的珠光体钢轨材料进行了轮轨滚动试验。结果表明，戈壁和沙漠中等强度沙尘暴环境下，随着钢轨硬度增加，平均黏着系数均无显著变化，车轮磨损率均先减小后增加，但钢轨磨损率在戈壁和沙漠中等强度沙尘暴环境下分别呈下降和上升趋势；这两种中等强度沙尘暴环境下，车轮的磨损机制主要为氧化磨损和疲劳磨损，且车轮氧化磨损随着钢轨硬度的增加而逐渐加剧，而钢轨的磨损机制主要为疲劳磨损；随着钢轨硬度的增加，这两种中等强度沙尘暴环境下，钢轨剖面裂纹深度总体均呈下降的趋势，表明钢轨的疲劳损伤随着钢轨硬度的增加而逐渐减轻；由于疲劳损伤对轮轨运行安全的影响比磨损更大，综合考虑钢轨材料的抗滚动磨损性能和抗滚动接触疲劳性能可以得出，高硬度的热处理钢轨更适合用于中等强度沙尘暴环境。     

表面硬化对地铁轮轨磨耗性能影响的实验研究

针对地铁轮轨的表面硬化问题,为了进一步降低轮轨的磨耗,通过对某实际运营线路中的钢轨和两种不同车轮钢的摩擦磨损进行实验研究,探讨了材料表面硬化对轮轨耐磨性的影响规律。首先,采用了赫兹模拟准则,对典型工况下地铁车辆的轮轨接触情况进行了模拟;然后,选取了某地铁线路现役的轮轨材料作为研究对象,并确定了其垂向载荷、运转速度和轮轨试样尺寸等实验参数;最后,采用GPM-60摩擦磨损实验机搭建了测试平台,进行了轮轨接触模拟实验,分析了表面硬化与地铁轮轨磨耗性能之间的规律。研究结果表明：车轮试样的磨耗率随表面硬化程度提高而下降,初始硬度较高的微合金化地铁车轮钢表现出更高的表面硬化程度和更好的耐磨性,相较于CL60钢,其磨耗率可降低35.1%,与其匹配的钢轨磨耗率可提高7.8%,轮轨总磨耗率可降低1.6%;建议在运营初期,对轮轨接触面进行喷丸强化处理,预先提高其表层硬度,以减少轮轨磨合阶段时间和初期磨耗量。     

不同工况下轮轨材料间的摩擦磨损行为

在MMS-2A型滚动摩擦试验机上研究了干态、水态和水砂态三种工况下轮轨材料间的摩擦磨损行为,分析了轮轨试样表面的损伤情况。结果表明:相比于干态,水会使轮轨材料间的摩擦因数、磨损量明显下降;水介质中撒砂可增加轮轨材料间的滚动摩擦因数和磨损量,且加重了轮轨表面的损伤,水砂态试验中的干摩擦会使摩擦因数恢复到干态下的正常水平;随水态、干态到水砂态工况的变化,车轮试样表面从粗糙凸起并伴有轻微剥落向严重剥落损伤转变,钢轨材料的表面损伤主要表现为片层状剥离并伴有剥落现象,但较车轮材料的剥落损伤程度轻。     

钢轨材料对滚动接触疲劳影响及高速铁路选轨研究

使用JD-1型轮轨模拟试验机针对淬火和热轧的PD3和U71Mn四种钢轨试样进行模拟试验,采用赫兹接触理论在实验室条件下模拟轮轨试样间的摩擦相互作用过程与现场中的相似.利用机械式光电分析天平通过称重法测量钢轨试样的磨损量,使用光学显微和扫描电子显微镜对钢轨滚轮试样进行微观分析,对高速铁路的钢轨选择提供依据.结果表明,材料硬度越高,磨损量越小,磨损面附近塑性变形层越薄,抗磨损性能越好,但高硬度材料裂纹扩展较深,疲劳损伤严重.硬度略低的材料,磨损量大,磨损面附近塑性变形明显,但由于部分刚萌生的微裂纹被磨去,疲劳损伤较为轻微.高速钢轨损伤主要以疲劳为主,U71Mn热轧钢轨有较好的抗疲劳性能,更适合于高速铁路铺设使用.     

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.