Running-in Test and Fractal Methodology for Worn Surface Topography Characterization

Studying and understanding of the surface topography variation are the basis for analyzing tribological problems,and characterization of worn surface is necessary.Fractal geometry offers a more accurate description for surface roughness that topographic surfaces are statistically self-similar and can be quantitatively evaluated by fractal parameters.The change regularity of worn surface topography is one of the most important aspects of running-in study.However,the existing research normally adopts only one friction matching pair to explore the surface topography change,which interrupts the running-in wear process and makes the experimental result lack authenticity and objectivity.In this paper,to investigate the change regularity of surface topography during the real running-in process,a series of running-in tests by changing friction pairs under the same operating conditions are conducted on UMT-II Universal Multifunction Tester.The surface profile data are acquired by MiaoXAM2.5X-50X Ultrahigh Precision Surface 3D Profiler and analyzed using fractal dimension D,scale coefficient C and characteristic roughness Ra ＊based on root mean square（RMS） method.The characterization effects of the three parameters are discussed and compared.The results obtained show that there exists remarkable fractal feature of surface topography during running-in process,both D and Ra ＊increase gradually,while C decreases slowly as the wear-in process goes on,and all parameters tend to be stable when the wear process steps into the normal wear process.Ra ＊illustrates higher sensitivity for rough surface characterization compared with the other two parameters.In addition,the running-in test carried with a set of identical surface properties is more scientific and reasonable than the traditional one.The proposed research further indicates that the fractal method can quantitatively measure the rough surface,which also provides an evidence for running-in process identification and tribology design.

Renovation and Rehabilitation Strategies for Worn-Out Texture of Ab-Anbar-No District in Sari Using SWOT Technique

Along with the growth and expansion of cities during the time, several parts of them have depreciated and they require repairing and inspection. Damaged places and repairing them are a problem that is significant and liable of each period has been looking for excogitation and resolving problems according to the existing circumstances. However, expressed concern that it is still a problem, is worn texture, which is extending fast in all cities of the world, particularly in developing countries, and this problem has gripped cities and authorities. In spite of all weaknesses and deficiency, since the majority of worn-out tissues have significant cultural, social and economic values which give identity to the cities, so paying attention to these areas and how to intervene in them is very important. The purpose of this paper is to study and consider ways of rehabilitation and renovation of the old texture of Ab-Anbar-No district in Sari, which it has been done using analytical-descriptive method. In this study, the needed information has been collected by observation, providing necessary map, library research and rehabilitation and reconstruction strategies have gained by SWOT model for analysis and internal factors (strengths and weaknesses) and external factors (threats and opportunities) of this tissue have been considered comprehensively. The results of this study show that strategies for rehabilitation and renovation of Ab-Anbar-No district are one part of the guidance, control and planning system of urban rehabilitation and modernization, as a guide for decision-making. The considered limitation of weakness and strengths in physical, environmental and functional fields have a high vulnerability and also have optimization opportunities in the economic, social and legal-administrative fields in order to take advantages for reaching perfection.

Worn surface characteristics of Cu-based powder metallurgy bake materials for aircraft

Cu-based powder metallurgy brake materials are used for aircraft widely and successfully.The characteristics of worn surface of Cu-based powder metallurgy brake materials for aircraft after working under service condition were studied,and two main wear mechanisms were discussed.The results show that the main components of worn surface are graphite,SiO2,Fe,Cu and oxide of Fe(Fe3O4 and FeO);the worn surface can be divided into three zones:severe wear zone,mild wear zone,and low wear zone; fatigue wear and grain wear are the main wear mechanisms of Cu-based materials.Some debris kept between brake discs reduce the wear rate to a certain extent by taking part in the regeneration of friction film.

Microstructures of worn surface and wear debris of as-cast Al-17Si-xLa alloys under unlubricated conditions

The tribological characteristics of hypereutectic Al 17Si x La alloys against heat treated GCr15 bearing steel under unlubricated conditions were investigated using a block on ring type wear testing apparatus in air at room temperature. Microstructures and chemical compositions of worn surface and wear debris were characterized by means of SEM with EDS and XRD patterns. XRD results show that wear behaviors of Al 17Si x La alloys are similar and the typical worn surface is characterized by smooth region and crater region. The mechanically mixed layer (MML) and the wear debris are very similar in microstructures and chemical compositions, both containing the fine equiaxed aggregates and large plates and blocks from the both sliding counterparts ( α (Al) and α Fe) and some reaction products (ternary oxides, i.e. Al Fe O and Fe Si O).

A novel approach to minimizing material loss for computer numerical control flank-regrinding of worn end mills

Flanks of end mills are prone to wear in a long machining process.Regrinding is widely used in workshops to restore the flank to an original-like state.However,the traditional method involves material waste by trial and error and dramatically decreases the potential regrinding.Moreover,over-cut would happen to the flutes of worn cutters in the regrinding processes because of improper wheel path.This study presented a new approach to planning the wheel path for regrinding worn end mills to minimize material loss and recover the over-cut.In planning,a scaling method was developed to determine the maximum size of the new cutter according to the similarity of cutter shapes before and after regrinding.Then,the wheel path is first generated by envelope theory to regrind the worn area with a four-axis computer numerical control grinder according to the new size of cutters.Moreover,a second regrinding strategy is applied to recover the flute shape over-cut in the first grinding.Finally,the proposed method is verified by an experiment.Results showed that the proposed approach could save 25%of cutter material compared with the traditional method and ensure at least three regrinding times.This work effectively provides a general regrinding solution for the worn flank with maximum material-saving and regrinding period.

周代裼袭礼辨疑

裼袭礼是周代典礼中常见的仪节之一,涉及周代贵族穿着裘衣之法、裘衣与裼衣色泽配合原则以及裼裘与袭裘的礼义等问题,《礼记》等屡有提及,而语焉不详。两汉以后,此礼亡佚,学者异说纷呈,莫衷一是。礼有“盛礼”与“非盛礼”之异,前者要求“充美”,后者则要求“见美”。裘衣之外加裼衣作为文饰,谓之“见美”;在裼衣外用另一件衣服覆盖,称为“袭”,谓之“充美”。裼袭乃是专为裘而设,因裘而有裼与袭,绝非专为聘礼而设。春、夏行礼,葛衣之外加罩衣,虽或有裼袭之义,但不得蒙裼袭之名。学者分歧之根源有二,一是郑注“裼者,免上衣见裼衣”与“凡襢裼者左”,所指非一,贾疏误混,并以为吉凶皆袒,后儒遂以丧袒、射袒、罪袒与裼袭之袒为一,致使经义淆乱。二是文字讹误,裼袭礼之“袒裼”当如段玉裁之说作“但裼”,如此则经义自清。《玉藻》入公门的规定可证表裘、袭裘乃未与裘服配合使用的裼衣、袭衣,袭衣确为充美之衣的专名。周代君臣礼服于细微处见名分,两国交聘,君臣同服麛裘,而主国之君以素衣为裼,使臣以绞衣为裼;裘服君用纯色,袖口处臣用杂色。三年之丧,丧服亦有相应之变化。

光纤扫描式李萨如轨迹近眼显示系统设计

为了进一步小型化头戴式显示装置(Head-worn Display,HWD),提出一种基于非对称光纤悬臂梁(Asymmetrical Fiber Cantilever,AFC)的李萨如轨迹扫描近眼显示系统,以及李萨如轨迹上的像素划分准则。研究了该系统的扫描轨迹、图像重建能力、显示分辨率和显示帧速率的影响因素。根据高分辨率、高帧速率指标设计了正交谐振频率组成,确定了非对称光纤悬臂梁的结构参数。研制的显示单元实物直径为2 mm,长度为19 mm。谐振频率下的分辨率为160×120 pixel,帧速率为10 Hz,图像重建误差率为0.002%,最高分辨率能够达到290×220 pixel,最高帧速率为95 Hz。基于显示单元实物搭建了光纤扫描式近眼显示系统,使用相机模拟人眼观察记录了该显示系统的实验结果,验证了基于非对称光纤悬臂梁的HWD显示性能及其未来应用潜力。

考虑轮轴过盈配合的地铁车轮踏面制动温度场和应力场研究

【目的】地铁车轮受力复杂,不仅受轮轨耦合力和轮-轴过盈配合产生的接触压力的影响,还受制动过程中产生的热载荷的影响。【方法】以某单S型辐板地铁车轮为研究对象,在ABAQUS软件中建立了地铁车轮有限元模型,分析了轮轴过盈配合对车轮在直线工况下机械应力分布的影响。建立了道岔工况下车轮踏面制动时的热-力耦合模型,采用直接耦合法研究了车轮温度场和应力场的变化规律,研究了不同磨耗量下车轮的机械应力和热-机耦合应力对车轮结构强度的影响。【结果】结果表明:制动时热载荷主要影响靠近踏面的结构部分,靠近轮毂部分受轮轴过盈配合影响大;新车轮与磨耗到限车轮辐板处的耦合应力最大相差69.3 MPa;车轮直径在820~840 mm区间内耦合应力比较稳定,浮动只有9.1 MPa.【结论】该研究为地铁车轮结构设计提供了科学的依据,对地铁车轮的维护工作具有良好的指导作用。

地铁车辆以磨耗车轮通过钢弹簧浮置板轨道时的较好平稳性速度

[目的]为使地铁乘客获得较好的乘车体验,探究轨道线路铺设浮置板时车体平稳性较好的通过速度区间。[方法]利用仿真软件建立了地铁车辆-浮置板轨道-路基的动力学模型,分析了标准车轮及磨耗车轮通过地铁有无钢弹簧浮置板轨道时的车体振动状况。对比了不同速度条件下,增设浮置板前后车体垂向平稳性指标时域及频域的变化;对比了车体在浮置板轨道系统下,车体以磨耗车轮与标准车轮通过时,车体的垂向振动加速度等参数时域及频域的变化规律。[结果及结论]不同速度时,浮置板会使列车的平稳性指标增大,相比无浮置板时平均增长了5.8%;横向平稳性指标在速度低于60 km/h时,其对平稳性指标有减小作用。浮置板系统中,磨耗车轮的存在会加剧车体垂向振动,这种现象在列车高速行驶时表现更突出。地铁车辆通过轨道时的垂向振动加速度频率主要集中在低频区段的0~10 Hz,横向振动加速度频率区段主要集中在0~30 Hz。地铁车辆通过存在浮置板路段且速度在48~60 km/h区间时,磨耗车轮的车体垂向平稳性指标在1.8左右,横向平稳性指标在1.1左右,数值均较低,即车体振动及横向运动较小,平稳性较好。

Research on Tribological Characteristics and Worn Surface Self-Repairing Performance of Nano Attapulgite Powders Used in Lubricant Oil as Addictive

As a kind of natural nanometer materials,the attapulgite has been widely used in industry,agriculture,environment,food substance,medicament and many other fields.Few researches about attapulgite used in lubricant oil as additive were made,and those were only at a preliminary stage of exploration.The tribological characteristics of attapulgite powders with the different contents added to CD 15W/40 lubricant oil were researched through"plane-on-plane"configuration friction and wear tester,and the self-repairing performance of 45#steel worn surface was examined via ring-on-block configuration test.XRD,SEM,EDS,TEM were employed to analyze the surface morphologies and elementary composition of the samples'worn surface.Furthermore,wear self-repairing mechanism of attapulgite additive to lubricant oil was explored.The results showed that:the optimal content of attapulgite powders in oil CD 15W/40 was 0.5 wt%,and the stable friction coefficient can be reduced to 0.02,then the friction reduction performance can be enhanced by 82.5%;Smooth worn surface were formed of the chemical reaction film containing elements O,Si,Fe;Friction reduction and self-repairing mechanism had a relation with the crystal structure of attapulgite.

数字化辅助全口磨耗牙咬合重建修复4年观察随访1例

磨耗牙的修复一直是口腔修复中的难点之一,本文报告全口磨耗牙病例1例,通过引入数字化咬合重建技术,利用虚拟性咬合引导开展系统性修复重建并随访4年,取得了较为满意的效果,该病例为数字化技术在磨耗牙的诊治提供了参考。

高精度工具磨床电主轴精度超差的原因及解决措施

针对某国产品牌电主轴在实际应用中易出现回转精度超差的问题,分析造成电主轴产生精度超差的主要原因是电主轴的气密封效果不佳,使得前端轴承及碟形弹簧进油受污染,从而导致电主轴前端轴承失效、轴芯磨损和拉刀力衰减过快。通过提升气密封压力值和改善轴芯材质及拉刀机构,解决了电主轴内部进油、轴芯磨损和拉刀力衰减过快的问题,使电主轴使用寿命提升1倍以上。

多模态数据融合引导的数字化种植和全口咬合重建

目的:探究应用多模态数据融合引导完成复杂数字化种植和全口咬合重建的可行性。方法:对一牙列重度磨耗伴牙列缺损的患者,获取并整合其口内扫描(intraoral scanning,IOS)、口外面部扫描(extral-oral face scanning,EOS)、锥形束CT(cone beam computed tomography,CBCT)及下颌运动等口颌系统的多模态数据,融合构建出四维虚拟牙科患者(virtual dental patient,VDP)。在四维VDP的引导下进行数字化种植和全口咬合重建,使用光学定位的下颌运动系统获取动态咬合数据,利用计算机辅助设计和计算机辅助制造(computer-aided design and computer-aided manufacturing,CAD/CAM)设计制作出最终修复体,完成全口咬合重建修复,并进行客观性评估。结果:该病例取得较好的修复治疗效果,患者对美观和功能满意,口颌系统健康、舒适。客观性评估数据显示,咬合重建后,患者牙尖交错位(intercuspal position,ICP)时的静态咬合和前伸、侧方运动时的动态咬合都得到了明显的改善,在前牙美学区和后牙功能区都取得了满意的治疗效果。结论:应用多模态数据融合引导完成复杂数字化种植和全口咬合重建具备可行性,值得推广。

暖季补饲矿物质盐砖对放牧牦牛瘤胃发酵和微生物区系的影响

为探究暖季补饲矿物质盐砖对放牧牦牛瘤胃发酵和微生物区系的影响,试验选取体重接近的2.5岁雄性牦牛12头,随机分为2组,每组6个重复,对照组纯放牧,盐砖组则采用放牧+补饲矿物质盐砖的饲养方式。结果表明:盐砖组牦牛瘤胃乙酸、丁酸、异戊酸、戊酸、总挥发性脂肪酸以及氨态氮的产量显著高于对照组(P<0.05),试验第30天对照组和盐砖组的瘤胃液pH差异不显著(P>0.05),试验第60天、90天盐砖组的瘤胃液pH显著低于对照组(P<0.05)。补饲矿物质盐砖能显著降低牦牛瘤胃甲烷杆菌、克里斯滕森菌科、克里斯滕森菌R-7等菌的相对丰度(P<0.05),显著提高了变形菌门、放线菌纲、红细菌科、纤维素单胞菌科等菌的相对丰度(P<0.05)。综上所述,暖季补饲矿物质盐砖能改变牦牦牛瘤胃微生物群落的活性,促进瘤胃发酵,提高牦牛生产性能。

弛张筛筛分效率与筛面磨损的匹配优化研究

为提高煤炭分选过程的生产效率,增加分选设备的使用寿命,最大限度地发挥选煤厂筛分设备潜在的生产能力,提高筛分工艺的合理性,以全面提升弛张筛筛分系统的筛分效率降低筛面磨损率,提出通过调节弛张筛性能参数的措施,使筛分效率达到最优,同时减小筛面的磨损。将柔性筛板离散化处理以降低柔性筛板仿真过程的复杂性,采用多体动力学仿真和离散元法耦合的方式,对筛面的筛分过程进行数值模拟,获得了弛张筛性能参数:弛张频率、筛面倾角、弛张量对筛分效率的影响规律,并综合考虑相关系数法和显著性检验方法,确定了弛张量为影响筛分效率的非关键因素。在总结了弛张筛筛分过程的磨损规律的基础上,通过Relative Wear和Archard Wear模型获得了仿真过程中筛面弛张量对磨损深度的影响规律。基于弛张量对筛分效率与磨损深度的双重影响,选用线性加权法进行筛面性能的多目标优化,获得了保证筛分效率最高磨损深度最小的筛面性能参数,并进行仿真验证。研究结果表明:筛分效率随筛面倾角的增大而减小,弛张量与弛张频率越大呈现先增大后减小的变化规律;筛面磨损与筛面弛张量同样呈先增大后减少趋势,综合考虑筛分效率与筛面磨损,获得了最优的筛面性能参数,即当筛面弛张量选择5 mm时,筛分效率可达到80.85%,而筛面磨损深度仅为0.0516 mm,相较于最优筛分效率时筛面磨损量减少了26.5%,而筛分效率仅降低0.48%,能够在对筛分效率影响较小的条件下显著降低筛面磨损程度。表明经过优化后的弛张筛筛分性能具有了明显的改善。采用上述技术方案能够有效提高分选过程中筛分环节的性能参数,提升设备生产能力,同时为选煤厂分选系统的智能化提供了技术支撑。

1种双配副摩擦试验机及其在多孔聚酰亚胺摩擦磨损测试方面的应用

在轴承中存在2类摩擦副,滚动体与内外沟道以及滚动体与保持架,尤其在采用聚合物保持架的轴承中,这2类摩擦副的性质完全不同,2类配副之间的相互影响不可忽略.目前,市面上的标准摩擦试验机均采用单配副,并不能很好地模拟轴承内部的摩擦.针对此问题,本文中研制了双配副摩擦试验机,并对该试验机进行了标定和校准.采用该试验机研究了多孔含油聚酰亚胺(iPPI)轴承保持架材料的发黑过程,对比了单配副和双配副下iPPI材料的摩擦磨损特性.结果表明,研制的双配副摩擦试验机能够较为真实地模拟保持架材料表面的磨损发黑现象,而单配副摩擦试验难以重现这种发黑现象.采用能谱分析(EDS)和拉曼(Raman)光谱分析单配副和双配副下iPPI的磨损表面,发现iPPI表面的发黑物质为α-Fe_(2)O_(3)和Fe_(3)O_(4).研制的双配副摩擦试验机测试精度高、重复性好,是1种模拟轴承内部摩擦的有效工具.

车轮多边形情况下轮轨接触算法

接触斑的法向应力分布是轮轨动力学分析和轮轨磨耗计算的基础。铁路车辆采用的磨耗型踏面出现多边形时,接触点处的轮轨横向曲率和纵向曲率都随接触位置的变化而变化,此时最常用的赫兹接触方法的精度难以保证。非赫兹方法的计算精度高,但其效率不能满足工程计算要求。应用非赫兹方法分析了车轮多边形引起的轮轨纵向曲率变化对接触斑的影响,发现当车轮多边形波长大于65 mm时,多边形对接触斑应力分布的影响可忽略不计。然后提出了改进的半赫兹方法,并对不同接触位置的接触斑形状和应力分布进行对比分析,结果表明:多边形波长大于65 mm时,改进的半赫兹方法在与非赫兹方法的结果保持一致的同时,大大缩短了计算时间。

基于GASF-CNN的高速列车转向架关键部件劣化状态识别研究

为研究高速列车转向架关键部件劣化状态的识别方法,通过统计抗蛇行减振器服役性能参数的分布特征,同时考虑阻尼和节点刚度变化组合形成5种劣化抗蛇行减振器试验工况,选取新踏面廓形和旋修后运行15万km、25万km的磨耗踏面廓形,进行了劣化状态下车辆动力学响应线路测试。基于实测数据,设计并构建基于GASF-CNN的转向架关键部件劣化状态分类辨识模型,以实测车体和构架横向加速度数据作为模型的训练集和测试集进行分类辨识模型训练,并对模型的泛化能力和识别准确度影响因素进行分析。通过优选数据构造方式、数据滤波、滑动窗口长度和数据通道数量,模型达到了较高的分类准确度,且对列车不同运行方向、不同速度级、不同运行环境等也达到了较好的泛化能力。

重载铁路货车轮径差与车轮圆周磨耗关系的试验研究

文中采用神华重载铁路模拟状态修运行试验数据,对运用20万km的C80型敞车车轮踏面圆周磨耗情况进行统计分析,比较初始设置不同轮径差、踏面圆周磨耗轮对运行20万km后轮径差分布和踏面圆周磨耗量的影响,并使用假设检验的方法对影响的显著性进行验证。

纳米金刚石在基础油中的摩擦学行为考察

在392 N,60 min,1200 r/min及75℃的试验条件下,用四球摩擦试验机对纳米金刚石在150N基础油中的摩擦学行为(减摩性能及抗磨损性能)进行了考察。在150N基础油(平均摩擦因数为0.099,磨损直径为0.908 mm)中分别添加10μg/g,25μg/g,50μg/g及100μg/g的纳米金刚石,其相应的平均摩擦因数依次为0.067,0.059,0.060及0.083,相应的磨损直径依次为0.775 mm,0.773 mm,0.835 mm及0.861 mm。纳米金刚石可以改善150N基础油的摩擦学行为,其最佳添加量为25μg/g,此时150 N基础油的减摩性能提高了40.40%,抗磨损性能提高了14.87%。