几种铝锡硅铜合金的摩擦磨损特性

采用环－块摩擦磨损试验机，考察了含Ｓｉ质量分数为１％～５％的Ａｌ－２０Ｓｎ－Ｓｉ－１Ｃｕ合金及传统的Ａｌ－２０Ｓｎ－１Ｃｕ合金的摩擦磨损性能．结果表明：几种Ａｌ－２０Ｓｎ－Ｓｉ－１Ｃｕ合金的磨损率低于Ａｌ－２０Ｓｎ－１Ｃｕ合金的磨损率，并且随Ｓｉ含量的增加而降低．干摩擦时，摩擦因数随Ｓｉ含量的增加无明显变化；油润滑时摩擦因数则随Ｓｉ含量的增加而略微减小．两类合金的摩擦因数均随滑动速度的增加而减小，随摩擦时间的增加先增加后减小并趋于稳定．磨损表面的ＳＥＭ分析表明：Ａｌ－２０Ｓｎ－Ｓｉ－１Ｃｕ合金在干摩擦下的磨损机制主要是磨粒磨损和氧化磨损，而Ａｌ－２０Ｓｎ－１Ｃｕ合金则包括粘着、疲劳及磨粒磨损等多种形式．在油润滑下，两者的磨损机理则分别为犁削作用和疲劳磨损及分层磨损．     

一种陶瓷刀具材料的摩擦损性能研究

ＴｉＢ２具有熔点高、硬度高和导热性、导电性及抗氧化性能都好等优点，在切削刀具、耐磨零件和某些特殊工况下使用的材料等方面的应用前景广阔．目前，含ＴｉＢ２的Ａｌ２Ｏ３基陶瓷刀具材料已经开发出来并投入实际应用，但对其摩擦磨损特性研究却还不多．因此，采用热压烧结工艺制备了Ａｌ２Ｏ３／ＴｉＢ２陶瓷刀具材料，在ＭＭ－２００型摩擦磨损试验机上，对不同ＴｉＢ２含量的增加，Ａｌ２Ｏ３／ＴｉＢ２陶瓷材料与淬火４５＃钢配副的摩擦学性能作了试验研究．结果表明：ＴｉＢ２的含量增加，Ａｌ２Ｏ３／ＴｉＢ２陶瓷材料的耐磨性明显提高，而摩擦系数仅略有上升，在切削加工淬火４５＃钢的过程中，Ａｌ２Ｏ３／ＴｉＢ２陶瓷刀具的抗磨能力比目前广泛使用的Ａｌ２Ｏ３／ＴｉＣ陶瓷刀具的高１倍以上．Ａｌ２Ｏ３／ＴｉＢ２陶瓷刀具材料的磨损机理主要是粘着、耕犁和脆性微脱落     

滚动轮波形磨损实验研究

利用赫兹模拟准则进行实验室钢轨波形磨损再现实验研究，在进行大量试验的基础上揭示了滚动轮波磨形成的规律，提出了波磨的形成机制．结果表明，轮—轨系统的振动以及轮—轨接触表面之间较大切向力的共同作用，是导致滚动轮表面不均匀塑性变形或波磨的主要原因．     

一种柴油机磨损的预测模型与试验研究

基于磨粒分析的油液监测技术，通常都偏重于从形态学方面进行研究，以获取单颗磨粒的“个体”信息，很少开展磨粒整体统计学方面的“整体”信息研究．其实，研究磨粒“整体”信息具有诸多优点，关键是如何从“整体”信息中获取反映摩擦学系统磨损状态转变和磨损程度分级的特征．通过在８ＮＶＤ４８Ａ－２Ｕ型柴油机上的现场监测试验研究，利用铁谱分析的ＤＬ和ＤＳ值，以及光谱分析的元素浓度值所包含的磨粒“整体”信息，建立了柴油机磨损程度的基准线，构造了磨损趋势校正的灰色预测模型，并且利用预测值和实测值的漂移值，设计了磨损趋势预测值的区间估计方法，以用于预报未来磨损的等级．这种基于磨粒“整体”信息的磨损预测方法，已用于８ＮＶＤ４８Ａ－２Ｕ型柴油机的实际监测，效果较好     

离心式渣浆泵叶轮磨损规律研究

在实验室条件下对离心式渣浆泵叶轮的磨损规律进行了研究，并对泵轮叶片间流道的颗粒运动轨迹进行数值模拟。探讨了磨粒浓度、泵转速、叶片几何参数、运行时间及磨粒粒径对泵轮磨损的影响。研究表明：叶片的磨损强度与泵轮转速呈５次方关系，叶片进口角对磨损强度影响明显，出口角对磨损强度影响不大，研究结果对渣浆泵的设计具有重要的参考价值。     

塑性变形对钢轨钢磨损影响的试验研究

塑性变形是铁路轮－轨在高接触压力下不可避免的现象，对磨损的发生和发展有重要影响，然而目前尚未见到塑性变形量有效测量方法的文献报道。通过对铁路轮－轨磨损的现场调查与试验研究，提出了一种新的磨损表面形貌测量法。     

工程粗糙表面粘着磨损的分形学研究

建立了分形接触模型,并在Ａｒｃｈａｒｄ粘着磨损理论基础上,结合磨损过程中剪切应力对实际接触表面的影响,建立了弹、塑性接触条件下的粘着磨损分形模型,通过试验得出了磨损体积损失与分形参数的关系,为降低磨损与加工成本及确定表面最佳分形维数提供了实验依据．     

Al^＋注入316奥氏体不锈钢表面改性的研究

利用６０ｋｅｖ的Ａｌ＋以４×１０￣（１７）ｉｏｎｓ／ｃｍ￣２的剂量对３１６奥氏体不锈钢进行了离子注入，并对注入前后之试样的显微硬度、摩擦磨损性能和电化学腐蚀性能进行了试验研究，还对Ａｌ”注入表面改性的机理作了探讨。结果发现，Ａｌ￣＋注入对３１６奥氏体不锈钢表面改性的效果很好，可以使其显微硬度提高４３．７％，摩擦系数降低约５０％，耐磨性能也有明显提高，同时还能使这种材料的腐蚀电流密度和腐蚀速率分别降低３个数量级和９个数量级。微观分析表明，注入的Ａｌ￣＋主要以替代方式存在于奥氏体结构中，改性层内大量替代式缺陷和空位型缺陷的存在造成了较大的晶格畸变，从而增强了固溶强化的效果。另外，由于铝和氧的亲和力很强，不仅容易在不锈钢表面形成氧化膜，而且还有助于磨损过程中氧化膜的形成与修复，因此，Ａｌ￣＋的注入能使３１６奥氏体不锈钢由粘着磨损转变为以氧化磨损为主的磨损机制。     

利用铝＋氮或钛＋氮离子束辅助沉积改善纯铁摩擦学性能的研究

离子束辅助沉积是近几年发展起来的一种将离子注入与薄膜沉积融为一体的材料表面改性新技术。利用Ａｌ＋Ｎ＋或Ｔｉ＋Ｎ＋离子束辅助沉积对工业纯铁进行了表面改性处理，并且就其摩擦学性能与未经表面改性处理之纯铁试样的作了对比试验研究，同时还利用俄歇电子能谱仪、掠角Ｘ射线衍射仪和扫描电子显微镜等分析测试手段对离子束改性层的成分深度分布和微观组织结构，以及磨痕的表面形貌和元素面分布进行了分析。结果表明，Ａｌ＋Ｎ＋或Ｔｉ＋Ｎ＋离子束辅助沉积可以在纯铁表面形成Ｆｅ４Ｎ、Ｆｅ３Ａｌ或Ｆｅ２Ｎ、Ｆｅ２Ｔｉ等强化相，因而使材料的表层显微硬度分别提高了２１．５％和５８．４％，稳态摩擦下的摩擦系数分别降低约８０％和８３％，平均磨损量分别降低约７１％和８６％；磨损形式主要由纯铁严重的粘着磨损转化为轻微的氧化磨损。     

ZA22—Al2O3复合材料干摩擦磨损表面的微观分析

用扫描电子显微镜和Ｘ射线光电子能谱仪分析了ＺＡ２２合金和ＺＡ２２－Ａｌ２Ｏ３复合材料在干磨擦条件下的磨损表面。结果表明：在ＺＡ２２合金磨损表面形成了一层厚约１００μｍ的塑性变形层，而添加Ａｌ２Ｏ３短纤维能够有效地使这种变形层减薄；在垂直于磨损表面的纤维周围的基础体明显比其它部位的高，磨损后复合材料表面的元素Ｚｎ被氧化，并有偶件材料的转移物存在。     

基于优化多核极限学习机的车轮多边形磨耗识别

多边形车轮是铁路机车车辆中普遍存在的一种磨损现象, 随着列车运营里程的增加, 车轮磨耗程度显著提升, 严重影响着列车乘坐舒适性和运营安全性, 借助于列车运营监测大数据开展多边形车轮动态检测方法研究具有重要意义. 本研究基于列车轴箱垂向加速度建立了多边形车轮定量识别模型, 首先通过阶次分析识别出轴箱加速度中包含的多边形车轮主要阶次, 同时获取各阶次对应的加速度幅值信息, 在此基础上引入加速度信号熵特征共同构建多边形车轮磨耗幅值识别特征矩阵, 然后建立遗传变异粒子群优化多核极限学习机 (GMPSO-MKELM) 识别模型, 通过特征矩阵与磨耗幅值的映射关系, 进一步实现了车轮多边形磨耗幅值识别. 通过仿真与现场实测数据研究结果表明, 所提出的识别模型能有效地从轴箱加速度中提取多边形车轮主要阶次, 磨耗幅值的识别精度均优于对比模型且具有较高的检测效率, 可实现均方根误差为0.0010 (仿真结果) 与0.0134 (试验结果) 的精确识别, 本文提出的多边形车轮磨耗识别模型可为列车车轮检测与智能维护提供理论基础.      

A simple mechanism for the polygonalization of railway wheels by wear

A mechanism is presented which explains the growing non-circularity of railway wheels by wear as a result of the interaction between the deviation from the circle and the rotational inertia of the wheels. The behaviour of the model is investigated by perturbation techniques, including the method of multiple time scales. Results conform with observations: The faster the train the quicker surge lower harmonics of the non-circularity. The procedure can be applied to study various other wear mechanisms even such where wear is influenced by locally variable material characteristics.     

Endurance study of bionic wheels for Mars rovers

Four kinds of bionic non-smooth surfaces were designed to improve the durability of wheels designed for Mars rovers. A durability test bed was developed, and the wheels were tested over different terrain conditions. Their performance was evaluated based on abrasion mass, energy consumption, and wear morphology. Convex domes exhibited optimal abrasive mass and energy consumption 46% and 16%, respectively, lower than with original wheels under coarse quartz sand conditions. When bedrock was added to the abrasive material, the abrasive mass and energy consumption of the convex dome and scale-like unit forms were reduced by 60% and 67.5%, respectively. These two non-smooth surfaces exhibited increased wear resistance and drag reduction. These results indicate that the durability of wheels can be improved using bionic optimization methods.     

Polygonalization of railway wheels

Summary A model of a flexible wheelset running on flexible rails is presented which demonstrates the growth of out-of-round profiles of the wheels. This process of growing is called polygonalization. We divide the model into two parts. One part describes the oscillations of the wheelset and the rails. The excitations, which are a result of the out-of-round wheels, are due to geometrical terms, while excitations of unsprung masses are not considered. The second part describes the development of the wheel profiles and the wear rate due to wear and hardening, respectively. The two parts can be coupled by means of perturbation theory with multiple-time scales, [4], [10] as a wear-feedback loop proposed in [6]. As the calculation show, the greater is the phase shift between the-out-of-round profiles of the right and the left wheel the faster the wheels become out-of-round. Furthermore, it is shown, that the first and the second bending modes of the wheelset play an important role in the growth of polygonized wheels. It should be emphasized that other reasons for polygonalization may exist too, e.g. excitations due to unsprung masses, [14]. Received 10 February 1998; accepted for publication 20 August 1998     

Interaction of subway LIM vehicle with ballasted track in polygonal wheel wear development

This paper develops a coupled dynamics model for a linear induction motor (LIM) vehicle and a subway track to investigate the influence of polygonal wheels of the vehicle on the dynamic behavior of the system. In the model, the vehicle is modeled as a multi-body system with 35 degrees of freedom. A Timoshenko beam is used to model the rails which are discretely supported by sleepers. The sleepers are modeled as rigid bodies with their vertical, lateral, and rolling motions being considered. In order to simulate the vehicle running along the track, a moving sleeper support model is introduced to simulate the excitation by the discrete sleeper supporters, in which the sleepers are assumed to move backward at a constant speed that is the same as the train speed. The Hertzian contact theory and the Shen- Hedrick-Elkins’ model are utilized to deal with the normal dynamic forces and the tangential forces between wheels and rails, respectively. In order to better characterize the linear metro system (LMS), Euler beam theory based on modal superposition method is used to model LIM and RP. The vertical electric magnetic force and the lateral restoring force between the LIM and RP are also taken into consideration. The former has gap-varying nonlinear characteristics, whilst the latter is considered as a constant restoring force of 1 kN. The numerical analysis considers the effect of the excitation due to polygonal wheels on the dynamic behavior of the system at different wear stages, in which the used data regarding the polygonal wear on the wheel tread are directly measured at the subway site.     

车辆纵向非光滑多体动力学建模与数值算法研究

在建立车辆纵向多体系统的动力学模型中, 将车身与车轮视为刚体, 两者通过减振器链接; 将传动系统视为一个圆盘通过扭簧和阻尼器与驱动轮连接; 将车轮与路面间的接触力简化为法向约束力、摩擦力和滚阻力偶,其中摩擦力的模型采用库仑干摩擦模型. 采用笛卡尔坐标作为该系统的广义坐标用于描述该系统的位形, 给出系统单双边的约束方程, 应用第一类拉格朗日方法建立了系统的动力学方程. 由于摩擦与滚阻的非光滑性, 使得该系统动力学方程不连续. 为便于计算, 建立了车轮与路面接触点的相对切向加速度与摩擦力余量的互补条件、车轮角加速度与滚阻力偶余量的互补条件, 以及车轮轮心法向加速度与路面法向约束力的互补条件. 将接触—分离、黏滞—滑移的判断问题转化成线性互补问题的求解, 并给出了具有约束稳定化的基于事件驱动法的数值计算方法. 最后, 应用该方法对车辆纵向多体系统进行了仿真, 分析了输出扭矩、摩擦及滚阻系数对其动力学行为的影响.      

汽车车轮流场的数值模拟

首先以独立车轮为研究对象,以商用计算流体力学软件STAR—CD为工具,利用移动边界条件,并依据k-ε双方程高雷诺数湍流模型对三维定常不可压缩流N-S方程进行数值模拟计算．然后在合适尺寸的计算域下对3种不同宽度的静止和滚动车轮分别进行数值模拟计算,研究车轮宽度和来流速度对阻力系数的影响,将计算结果与实验结果进行了对比分析．计算结果表明,车轮宽度的减小以及来流速度的减小均明显降低汽车的气动阻力系数．     

预混燃气高压不稳定燃烧实验研究

以冲压加速器为工程背景,着重研究预混燃气高压不稳定燃烧问题。采用实验方法,分析预混燃气装填压力、配比等因素对不稳定燃烧的影响;采用频谱分析方法,分析诸因素对压力振动特性的影响。实验给出的预混燃气的装填压力及配比的范围,可直接应用于冲击加速器射击实验,这对于减少冲压加速器高压异常事故具有重要的实际意义。     

Computational dynamics: theory and applications of multibody systems

Multibody system dynamics is an essential part of computational dynamics a topic more generally dealing with kinematics and dynamics of rigid and flexible systems, finite elements methods, and numerical methods for synthesis, optimization and control including nonlinear dynamics approaches. The theoretical background of multibody dynamics is presented, the efficiency of recursive algorithms is shown, methods for dynamical analysis are summarized, and applications to vehicle dynamics and biomechanics are reported. In particular, the wear of railway wheels of high-speed trains and the metabolical cost of human locomotion is analyzed using multibody system methods.     

车轮材料特性对轮轨磨损与疲劳性能影响的研究

在MMS-2A滚动摩擦磨损试验机上进行不同材料车轮与U75V热轧钢轨的匹配试验,研究材料特性对轮轨试样磨损与疲劳性能的影响.结果表明:随着车轮碳含量增加,组织中珠光体比例增加,珠光体中渗碳体片层间距减小,硬度增大;随着轮/轨硬度比增大,车轮表层的塑性变形层厚度逐渐减小,对摩副钢轨塑性变形层厚度呈现先增大后减小的趋势;车轮试样磨损形式由小剥离掉块向大剥离掉块转变,钢轨磨损机制由材料表层的轻微剥落向深层剥落磨损转变;提升车轮的硬度,轮轨表面的疲劳裂纹长度减小;且随着车轮硬度的增大,钢轨表面萌生的疲劳裂纹的末端扩展角度有增大的趋势,使钢轨的疲劳裂纹更容易向材料心部扩展.