弓网系统滑动电接触表面磨损特征研究

为探究弓网系统受电弓滑板在不同电流、接触压力和滑动速度条件下的磨耗特性,开展弓网载流磨损实验,探讨不同工况下摩擦副的载流效率、电弧能量、摩擦因数和温度;分别使用金相显微镜与表面粗糙度仪对实验后的滑板磨损区域进行分块多次测量,使用一种基于Otsu大津算法的图像处理方法,将凹坑部分从形貌图像中提取并进行标记计算,统计分析不同工况下凹坑面积、数量和粗糙度参数（包括轮廓算术平均偏差和最大轮廓谷深）的变化情况。结果表明：随着电流的增大,凹坑面积和数量增加,粗糙度参数减小;随着接触压力的增大,凹坑面积减小,凹坑数量先减小后略有增大,粗糙度参数减小;随着滑动速度的增大,凹坑面积、数量和粗糙度参数都增大。     

苜蓿草粉对金属材料磨损表面的分形维数计算

基于分形理论和扫描电镜分析,采用差分计数盒法(DBC)计算了苜蓿草粉对金属材料磨损表面的三维分形维数。结果表明:基于DBC法和磨损表面SEM照片计算所得的分形维数,可以表征苜蓿草粉对金属材料磨损表面的形貌特征;相同加工条件下的金属加工表面具有相近的分形维数,但不能通过分形维数区分材料;苜蓿草粉磨损后的磨损表面分形维数与磨损体积损失有着密切的关系,体积磨损量越大,分形维数也越大。     

Wear behaviour in the presence of magnetic fields for pin-on-disc repeated dry wear tests

Wear behaviour in a magnetic field is discussed for pin-on-disc repeated dry wear tests.The results showed that the sliding distance corresponding to a severe-mild wear transition decreased with increasing magnetic flux density. Consequently, the degree of wear also decreased in the presence of a magnetic field. These phenomena were observed, remarkably, for the case using a carbon steel pin, which is a material that easily oxidizes. To discuss the above phenomena, the oxidation of steel filings in a magnetic field was investigated at high temperature. As a result, it was certain that the activation energy for oxidation decreased both in ac and dc magnetic fields. EPMA observations also proved that the magnetic field promoted oxidation.It was concluded that the degree of wear decrease was caused by magnetic-field-promoted oxidation of wear particles and these oxidized fine wear particles existed and attached to the wear surface owing to the magnetic forces present.     

基于表面灰度图像的植物磨料磨损表面分形维数计算

以磨损表面SEM灰度图像为研究对象,采用变分法、双毯法、差分盒计数法和盒计数法4种方法计算植物磨料对不同金属材料磨损表面的三维分形维数。结果表明:植物磨料对金属材料磨损表面具有分形特征,分形维数与体积损失有着密切关系,体积磨损越大,分形维数也越大。4种算法中,变分法计算的分形维数稳定性最好,其次是双毯法和差分盒计数法,盒计数法对表面噪声最为敏感。     

表面粗糙度对滑动电接触磨损率的影响

在电气化铁路弓网系统中,磨损率是衡量列车运行状态与接触导线使用状态的重要指标。为了充分模拟弓网系统中磨损率情况,利用自行搭建的滑动电接触摩擦磨损试验机对滑板和接触导线进行摩擦磨损试验,分析滑板表面粗糙度、法向压力、接触电流与运行速度对磨损率的影响。得出结论:滑板磨损率随滑板初始表面粗糙度、接触电流、法向压力、运行速度的增加而增加,而高载荷下粗糙度对于磨损率的影响降低;滑板摩擦从磨合期进入稳定摩擦期存在一个临界表面粗糙度,当滑板初始表面粗糙度值等于临界粗糙度值时,其磨损率最低;不同初始表面粗糙度的滑板在跑合期内磨损过程不同,在稳定摩擦期内磨损过程趋于一致,且摩擦试验后滑板表面粗糙度也接近。     

基于响应面法和蒙特卡罗法的齿轮热弹耦合接触特性研究

首先运用摩擦学、传热学和有限元法研究了齿轮的本体温度场,然后利用间接耦合法对齿轮进行了结构分析,以齿轮材料的线膨胀系数、油温、主动轮转速、主动轮功率及齿面许用接触应力为随机变量,基于响应面法得到了齿面接触强度的极限状态函数,并通过蒙特卡罗法得到了各随机变量对该极限状态函数的概率敏感性。结果表明,响应面-蒙特卡罗法有效简化了复杂结构的可靠性灵敏度分析。     

不同刹车压力下C/C复合材料的摩擦性能与摩擦面研究

采用MM-1000型摩擦磨损试验机对以光滑层、粗糙层为基体炭的2种C/C复合材料在不同刹车压力下的摩擦磨损性能进行了测试。借助微区拉曼光谱和扫描电镜对其摩擦表面的石墨化度与形貌进行了分析。结果表明：以粗糙层为基体炭的C/C复合材料比以光滑层为基体炭的C/C复合材料有更优异的摩擦压力或温度特性。微区拉曼光谱检测证实在摩擦面上粗糙层基体炭相对光滑层基体炭更易变形,所以以粗糙层为基体炭的C/C复合材料的摩擦面在刹车压力达到0.59 MPa时便能形成较厚的摩擦膜,故其摩擦因数能在较高刹车压力下（1.05-1.82 MPa）保持较高的稳定值（0.31）,且磨损适当;而光滑层基体炭C/C复合材料需在刹车压力超过0.82 MPa时摩擦面才能形成较薄的摩擦膜,并且由于其导热系数低,高压刹车时摩擦表面氧化严重,所以高压刹车时其摩擦因数衰减大,线性磨损率大,尤其是质量损失急剧升高。     

润滑点接触粗糙表面滑动摩擦因数的实验研究

利用多功能微摩擦试验机,在轻载荷条件下测量了具有横向纹理圆盘表面的摩擦因数,得到了包括流体润滑、混合润滑和边界润滑完整的Stribeck曲线。考虑了载荷和时间对实验结果的影响,对不同粗糙度表面的Stribeck曲线进行了比较。实验的初步结果表明:增加载荷与实验时间,会获得更加稳定的实验结果;表面越粗糙,从混合润滑向流体润滑转换的临界速度越大;表面越光滑,Stribeck曲线的“谷底”越明显。     

直流稳恒磁场对45~#钢磨损性能的影响

大气条件下,研究了低强度直流稳恒弱磁场对45#钢干滑动磨损性能的影响.结果表明:与无磁场条件下相比,直流稳恒弱磁场使45#钢磨损量明显减少;随着磁场强度的增加,磨损量逐渐减少.3-D表面形貌分析表明,施加一定强度磁场的试样磨损后,表面光滑平整.     

考虑表面粗糙度的面齿轮齿面接触应力分析

根据齿轮啮合原理,得出了面齿轮的齿面方程,求得面齿轮齿面曲率。结合赫兹接触理论,推导了点接触面齿轮传动接触点的接触应力及应力沿齿面的分布规律,从齿根到齿顶,齿面接触应力先增大后减小,在靠近齿面中点处达到最大值。由粗糙表面接触理论,分析了面齿轮齿面微观弹塑性变形时的接触面积,并得到粗糙齿面接触时面齿轮齿面接触应力及其分布。对比分析了几种不同粗糙度条件下面齿轮齿面接触应力的变化规律,结果表明:齿面接触应力随表面粗糙度的增大而增大,与齿根处相比,齿顶接触应力受表面粗糙度影响更大。文中的分析可为面齿轮磨损及润滑机理的研究提供依据。     

碳钢渗硫表面低副接触模型及其塑性指数

制备了渗硫试件，测量了渗硫层的显微硬度及弹性模量等力学性能参数。建立了渗硫面与非渗硫面的多球凸峰面接触模型，其凸峰高度为高斯函数分布。在此基础上计算了不同接触情况下的塑性指数ψ，其范围在4—15之间，所以渗硫面接触主要为塑性接触。     

Study of the Regenerated Layer on the Worn Surface of a Cylinder Liner Lubricated by a Novel Silicate Additive in Lubricating Oil

Some special silicate particles as additives in lubricating oil have shown a certain self-repairing function for the rubbing pairs of industrial equipment in recent R&D of extreme pressure antiwear additives. This article introduces an investigation on the regenerated layer on the worn surface of a practical cylinder liner lubricated by lubricating oil with a silicate additive using some advanced techniques like transmission electron microscopy (TEM), atomic force microscopy (AFM), nano-hardness tester, scanning electron microscopy (SEM), auger electron spectroscopy (AES), and Raman spectroscopy. The basic formula of the mineral in the silicate additive is Al₄[Si₄O₁₀](OH)₄. Through some macro- and microanalyses, it was found that the silicate additive showed an obvious improving effect on their friction surface and self-repairing function. The roughness of the worn surface could be decreased greatly to several tens of nanometers, and its hardness was still above 10 GPa. The worn surface with some pits and cracks had been covered by a transparent regenerated layer, and the wear of cylinder liners was maintained at almost zero-wear level on average. The mechanism of the self-repairing function was approached. It was revealed that the silicate additive was acting as a catalyst to promote a series of complex tribochemical reactions to form a regenerated layer with amorphous carbon structure on the worn surface under high-friction temperature and pressure in the friction and wear process.     

考虑两粗糙面分形特性的接触模型

基于M-B分形接触模型,通过构建接触系数建立了考虑两粗糙面分形特征的接触模型。分析结果表明,修正模型能较好地与实验数据相吻合,并适用于更大的载荷,修正模型综合考虑两粗糙面的特性,其计算结果与实际接触情况更相符,为摩擦磨损预测、磨粒分析以及不同粗糙度表面的接触分析提供了参考。     

钢球滚子弧面凸轮分度机构的接触应力分析

运用回转张量法推导出凸轮廓面方程和啮合方程，并进一步计算了该机构啮合曲面的接触应力。     

低碳微合金钢中厚板表面裂纹形成原因分析

分析了中厚板表面裂纹形成的原因.结果表明:中板表面裂纹是连铸坯表面裂纹的遗传,连铸结晶器内坯壳不均匀是导致裂纹产生的根本原因.通过降低C含量、更换镀层结晶器等措施,取得了良好的效果.     

铸钢件表面铬合金层形成机理

在测试合金粉膏块内外界面上温度变化的基础上，计算了合金层的热扩散率，绘制了合金层及砂型截面上温度场分布，以此预测并验证了络合金层最低烧结温度为1280℃。     

Surface Texturing and Alternative Lubricant: Tribological Study of Tapered Die Sliding Contact Surface in Cold Extrusion Process

Recently, there is greater concern for industries to maintain lubricant flow along the extrusion process, which is important to obtain the best quality of the final products. One of the most cost-effective methods is surface texturing. In this research, surface texturing was embedded on a tapered die sliding contact surface to explore its effectiveness on a finished product from a cold extrusion process. Palm oil–based lubricant was tested for cold extrusion processes and mineral oil was used for comparison purposes. It was found that a textured tapered die (TA) performed a diminished extrusion load compared to an untextured tapered die (NA) and improved the performance of other test parameters. As an alternative lubricant, refined, bleached, and deodorized (RBD) palm kernel oil presents results similar to those of commercial extrusion oil in terms of extrusion load and product quality. Based on the results, it is proven that surface texturing and palm oil–based lubricant can be considered as an alternative approach for implementation in industry.     

表面纳米化40Cr钢的组织特征

采用超音速微粒轰击方法对40Cr调质钢进行了表面纳米化处理。X射线衍射、透射电子显微镜和纳米压痕试验结果表明，表面纳米化层深达20μm，平均纳米压痕硬度比纳米化前提高2倍以上，达到8．0GPa。在表面纳米化试样表面至250μm的区域内存在残余压应力，最大残余压应力位于表面纳米化层与过渡区的分界线附近。     

表面粗糙对乏油条件下非牛顿点接触热薄膜润滑的影响

假设运动表面为光滑表面,静止表面上有一个垂直于卷吸速度方向的横向划痕,采用Ree-Eying本构关系求解表面单一粗糙对纯滑动点接触热薄膜润滑的影响,分析处于接触区中心的表面划痕在不同的乏油程度下对油膜压力、膜厚及温度的影响。结果表明:在乏油条件下,处于静止表面上接触中心的横向划痕前后的压力和温度都有尖锐的升高,且这种升高幅度随乏油程度的严重而增加;在乏油条件下,表面粗糙的存在更不利于润滑,易于造成润滑失效。     

非调质钢35MnVN强化状态滑动磨损特性的铁谱分析

本文应用铁谱技术对非调质钢３５ＭｎＶＮ及调质钢４０Ｃｒ，４５号钢强化状态的磨损过程进行了分析比较，结果表明：在滑动磨损条件下，３５ＭｎＶＮ强化状态的耐磨性优于４０Ｃｒ，４５号钢质后强化态的耐磨性，说明在滑动磨损工况下非调质钢３５ＭｎＶＮ完全可以取代调质钢４０Ｃｒ，４５号钢使用。