磨合试验及磨合吸引子初探

为了表征磨合过程和磨合状态,掌握磨合过程中表面形貌的变化规律,在销-盘式试验机上对45#钢摩擦副进行了润滑条件下的磨合试验,用T1000型表面粗糙度测量仪和计算机数据采集系统测量磨合过程中的表面形貌和粗糙度值,并用分形方法对表面形貌进行分形表征和分形参数计算。研究表明:随着磨合过程的进行,摩擦副表面的粗糙度和分形参数逐渐变化,当达到磨合状态时,2个表面具有互适匹配的稳态参数值。因而从非线性科学原理出发,将磨合过程当作摩擦学系统的自组织过程,提出磨合吸引子的概念,并进行了初步的探讨。     

Ultralow Friction Between Steel Surfaces Achieved by Lubricating with Liquid Crystal After a Running-in Process with Acetylacetone

A suitable running-in process is advantageous for reducing friction. The aim of the present work was to study the influence of the running-in with acetylacetone on tribological performance of 4-Cyano-4’-pentylbiphenyl (5CB) liquid crystal. Friction tests were performed between steel surfaces in a ball-on-disk sliding system. After a running-in period of 240 s, the COF of 5CB was measured to be 0.013, which is about a quarter of the value (0.055) without running-in. The reduced contact pressure, caused in running-in process, does not directly lead to a drop in COF. The generation of tris(acetylacetonato) iron(III) induced by the tribochemical reactions between acetylacetone and steel surfaces, and the unique physical properties of liquid crystal are assumed to be reasons for the ultralow COF. Surface analysis was performed to correlate COF with the topography of wear surfaces. An evenly distributed specific grooved structure observed on wear area of the ball may have a beneficial effect on COF as well. We believe our findings can provide an effective and simple solution to reduce COF of liquid crystal between steel surfaces. A better understanding of the tribological behavior is needed for the development of this tribological system and for the possible future applications.     

磨合油对柴油机磨合过程的影响研究

应用表面粗糙度分析仪、发射光谱和扫描电镜等,利用油液检测技术,结合使用不同的磨合油,对CA6110Z-07Y型柴油机磨合过程进行综合研究。实验结果表明：使用专用磨合油后柴油机所有磨损性元素的含量在25-30min。后呈下降趋势,说明柴油机摩擦副在25-30min后已完成磨合过程;使用专用磨合油能有效改善摩擦副表面性能;台架磨合与摩擦副的原始表面粗糙度关系不大;利用润滑油分析技术和其它磨合技术,不但可以降低磨合过程的故障率,提高磨合质量,而且可以将该机型的磨合时间由45min缩短到25-30min。     

齿轮磨合技术研究

以磨合机理研究为基础,以齿轮承载能力对齿面磨合技术的相依性为出发点,着重用一系列模拟试验的方法,研究齿轮磨合表面粗糙度规律及齿轮磨合过程控制规律,以便发挥磨合技术对于提高齿轮承载能力、传动效率以及对于延长工作寿命的重要作用。     

Boundary film formation from overbased calcium sulfonate additives during running-in process of steel–DLC contact

The initial stage of boundary film formation from overbased calcium sulfonate at steel–DLC (diamond like carbon) contact was studied. A running-in process was clearly observed by the combination of fresh DLC with fresh steel or fresh DLC with rubbed steel. On the other hand, rubbed DLC does not possess the running-in process. Surface analysis by TOF-SIMS was applied to investigate the formation process and structure of films. It was found that the transfer of iron from the steel ball on to the DLC surface plays a significant role in the formation of boundary film. The depth profile of the film was also obtained by means of an etching technique. The boundary film on steel ball and DLC are mainly composed of iron and calcium oxide. However the depth profiles indicate that distribution of calcium oxide on steel ball is different from that on DLC coated disk.     

磨合添加剂对内燃机缸套珩磨的影响

利用MPX-2000型盘销式摩擦磨损试验机,研究了磨合添加剂T301和T321及其复配后对20钢缸套的珩磨效果;采用SHIMADZU SSX-550型扫描电子显微镜观察20钢试件的磨损表面形貌。结果表明：两种磨合添加剂添加量在质量分数为20％时,缸套的磨损量最大,并且添加T321时的磨损量是添加T301的3倍;在完成的实验中,T301和T321复配的最佳比例为10％T301＋10％T321;磨合添加剂对20钢缸套的珩磨主要发生的是摩擦化学（腐蚀）磨损。     

纳米铜对车用柴油机磨合过程的影响研究

从改善车用柴油机台架磨合质量,缩短磨合时间的角度出发,利用油液检测光谱分析技术和扫描电镜分析,对CD40润滑油及添加纳米铜的CD40润滑油进行实车台架磨合试验。实验结果说明使用添加纳米铜的CD40润滑油的2#柴油机在台架磨合25 m in时,柴油机主要磨损性元素Fe、Pb和A l就处于平衡状态,而使用CD40润滑油的1#柴油机在台架磨合结束时,上述各元素仍处于上升趋势。试验结果证明纳米铜添加剂能够有效改善柴油机的磨合质量,缩短磨合时间。     

复合润滑结构表面在油润滑下的减摩性能*

为研究不同表面处理方式对巴氏合金/45钢配副表面减摩性能的影响,采用热压固化工艺将六方氮化硼封装于表面织构内,制备复合润滑结构表面;在油润滑下进行销-盘磨损试验,使用递归定量分析（Recurrence quantification analysis,RQA）参数划分磨损过程;研究复合润滑结构表面在磨合期和正常磨损期的减摩性能,并与纯织构表面减摩性能进行对比。结果表明：复合润滑结构表面拥有较低摩擦因数和显著减摩效果,其减摩性能优于纯织构表面;相比无织构表面,复合润滑结构表面在磨合期内的平均摩擦因数下降77.9%,在正常磨损期内的平均摩擦因数下降73.5%且磨合期的时长缩减75.0%;较大织构孔径的复合润滑结构表面的减摩效果更好且磨合期更短;纯织构和复合润滑结构表面的减摩效果均在较高速度和载荷下更显著;各试样表面在磨合期的摩擦因数越低,对应进入正常磨损期后就越低。     

Tribological behaviour of MW PACVD diamond coatings in vibrating contacts

Six diamond coatings were produced by microwave plasma-assisted chemical vapour deposition (MW PACVD) on polished SiC substrates. Process gas pressure and process gas composition were varied systematically, resulting in different coating morphologies, roughnesses and grain sizes. Friction and wear were investigated for unlubricated vibrating contact conditions in air at room temperature. Tribological tests on diamond coatings were performed in a ball-on-disc configuration, with steel balls (100Cr6) and alumina balls acting as counterbodies. For comparison of the tribological performance of the diamond coatings, standard tests were performed with a stroke of 200 μn, a load of 10 N, and a frequency of 20 Hz. The effect of relative humidity (RH) was investigated by testing in dry (3% RH), in normal (50% RH), and in moist air (100% RH), respectively To investigate running-in effects and wear propagation, the test duration (10⁴, 10⁵, and 1.2·10⁶ sliding cycles) was varied. For steel/diamond pairings, high wear at the steel ball and high friction were measured, influenced by roughness and grain size of the diamond coating and by relative humidity. For Al₂O₃ against diamond, a pronounced running-in of friction and wear was found. High friction and high wear at the beginning of each test are followed by a stationary phase with extremely low friction coefficients (⩽ 0.05) and with wear rates below the limit of resolution. This running-in depends on grain size and roughness of the coating, on relative humidity, as well as on the operational parameters. Surface analysis using SEM, EDX, LRS and AFM was conducted, to investigate tribologically induced surface changes.     

Influence of Surface Roughness on the Transfer Film Formation and Frictional Behavior of TiC/a-C Nanocomposite Coatings

Influence of surface roughness on the friction of TiC/a-C nanocomposite coatings while sliding against bearing steel balls in humid air was examined by detailed analyses of the wear surfaces and the wear scar on the ball counterparts by atomic force microscopy, optical, and confocal microscopy. It was observed that the surface roughness of the coatings essentially determines the wear behavior of the ball counterpart, which consequently influences the transfer film formation. A rough coating causes abrasive wear of the steel ball during the running-in period, which impedes the formation of a stable transfer film and leads to higher values of coefficient of friction (CoF). Moreover, the CoF does not show a decreasing trend after the running-in period, although the roughness of the coating was greatly reduced. Replacing the worn ball with a new one after the running-in period yields lower CoF values similar to that observed for a smooth coating. In both of the cases, no wear of the steel ball occurs and a stable transfer film forms and effectively covers the contact area. The influence of the wear debris on the formation of the transfer film is also discussed.     

Remarkable effects of running-in upon surface durability of steel and bronze

The authors have shown that, in order to obtain a pitting limit higher than 0.5 times the Brinell hardness, the nearly full elastohydrodynamic lubricating (ehl) oil film must be formed at an early stage of loaded running. However, it was almost impossible to obtain a full ehl oil film without running-in at Hertzian stresses higher than 1000 MPa in the case of metal rollers made from two representative materials, ie a low hardness steel and a phosphor bronze. The progress of running-in was affected deleteriously by a few small protrusions on the harder surface with different hardness combinations, or a hard spot with nominally equal hardness combinations (rolling pairs). This paper demonstrates how and why the few protrusions or the hard spot occupying an area less than 0.2% of the total contact surface can prevent the completion of running-in, ie the formation of the full ehl oil film. The reduction in the rate of running-in can cause pitting due to the accumulation of the fatigue damage before emergence of the beneficial effect of running-in     

The generation and properties of boundary films formed by diesel fuel at a steel/steel conjunction

Thin gel-like films are seen on the lubricated surfaces within diesel fuel injection equipment. The formation and properties of these films are investigated, under sliding conditions, using disc-on-plane machines; one steel has been used throughout. The development and maintenance of separation is measured by voltage drop and, during running-in to a high conjunction resistance, films are produced which are similar to those seen in practice. It is shown by static tests that separation is maintained by these films, which behave as quasi-elastic solids. The films are not miscible with diesel fuel and are not produced when the fuel is in static contact with the steel. They exhibit similar electrical properties under static and dynamic conditions: this was unexpected and is not yet understood. It is postulated that the films are produced by chemical reactions, and that the surface polishing observed is due to the same reactions     

The combined effects of ZDDP, surface texture and hardness on the running-in of ferrous metals

The effects of surface characteristics including roughness, lay direction and hardness of rubbing pairs on the antiwear performance of secondary short chain ZDDPs under a boundary lubrication condition are studied experimentally. The antiwear performance of the ZDDPs is evaluated by the duration of running-in periods recorded in wear tests of specially prepared specimens. A running-in period is defined as the time interval from the beginning of a wear test to the time at which the contact resistance between the rubbing pair approaches infinity. The shorter running-in period yields the better antiwear performance. The wear tests were conducted with a reciprocating sliding contact made by flat-on-flat specimens which were made from grey cast iron, quenched medium carbon steel and bearing steel. Two lay directions of the surface texture, namely, parallel and perpendicular to the sliding direction were ground, which made four possible combinations in a rubbing action. The CLA roughness of the specimens ranged from 0.35 μm to 0.04 μm. It is found that to obtain a shorter running-in period and to enhance the antiwear performance of ZDDPs, the following rules should be obeyed. If the hardness numbers of the two rubbing members are near the same, the combination of their lay directions should be both in parallel but perpendicular to the sliding direction and, the roughness values should be smaller than 0.09 μm. If the hardness number of one member is much greater than that of the other, the soft member should be the smaller one and the surface of the hard member should be as smooth as possible. Under any circumstance, the smaller members should be chamfered.     

Experimental and theoretical investigation of running-in

In this paper, the running-in and steady-state wear in the mixed-EHL line contact problem are analytically and experimentally studied. An experimental apparatus is designed and built to investigate the transient wear process during the initial stage of contact of two rollers with fresh surfaces as well as the contact of broken-in surfaces, when wear rate becomes steady. Seven experiments are conducted with five running-in experiments on fresh rollers and two steady-state experiments on the run-in rollers. The results of experimental tests and a series of simulations of an analytical model that uses the load-sharing concept and accounts for plastic deformation of asperities during the running-in stage are presented. The comparison of experimentally measured wear weight, wear depth, surface roughness, friction coefficient, and surface temperature of these seven experiments are shown to be in good agreement with the simulation results.     

Prediction of Surface Topography at the End of Sliding Running-In Wear Based on Areal Surface Parameters

Running in is a complex process, and it significantly influences the performance and service life of wear components as the initial phase of the entire wear process. Surface topography is an important feature of wear components. Therefore, it is reasonable to investigate the running-in process with the help of surface topography for improvement. Because the surface roughness after running in is independent of the nature of initial roughness, it is difficult to predict the surface topography after running in based on unworn surface topography. Aiming to build a connection of surface topographies before and after the running-in process, a black-box model predicting surface topography after the running-in process was established based on least-squares support vector machine (LS-SVM), and the areal surface evaluation parameters were adopted as model variables. To increase the adaptability of the predictive model, the main factors of the work condition were also taken into consideration. The prediction effect and sensitivity of the model were tested and analyzed. The analysis indicates that the hybrid property of surface topographies before and after running in is closely related. Moreover, the surface topography after running in is influenced more by the initial surface topography than by the work condition.     

磨合过程中表面形貌变化的分形表征

磨合是各运动副在投入运行前为获得好的配合性、提高承载能力所必须经历的过程,表面形貌的明显变化是磨合过程中表现出的重要特征。本文引入分形理论,用分形参数表征磨合表面的形貌变化。研究表明,磨合表面变化的分形参数表征是简单有效的。     

润滑油光谱分析特征信息研究

光谱分析技术是基于油液检测的机械设备故障诊断和分析零件失效的主要手段和方法,而为了建立基于油液检测故障诊断专家系统所必需的知识库,要求对获得的光谱分析数据进行真实准确的信息提取,并能够提供相应的数学模型,以便于信息的识别。本文对油液检测手段中的油料光谱分析进行描述,分别建立了光谱分析的元素质量分数、相关元素质量分数比、元素质量分数梯度、相关元素质量分数梯度比4个参数。将建立的4个参数用于柴油机台架磨合试验数据的分析,表明光谱分析特征信息可以较好地反映柴油机磨合过程,实现了对柴油机台架磨合过程的状态监控。     

A Novel Running-in Method for Improving Life-Time of Bulk-Fabricated Silicon MEMS Devices

A running-in process is usually intentionally employed as an effective way to make friction pairs in macro-scale machinery more suitable for heavy load conditions. For silicon-based microelectromechanical systems (MEMS) with rubbing parts, however, even a short-time period of running-in under air or nitrogen environment can induce severe damage on rubbing surfaces, which prohibits any possibility of continuing operation. In this article, we demonstrate a new running-in process for MEMS devices, which can effectively reduce undesirable initial wear and thus generate an endurable bearing surface. The new running-in process consists of two steps of tapping treatment. A home-made microfriction test system has been developed to evaluate the effectiveness of this method. Through the tapping treatments, bearing spots on the rubbing sidewalls are restricted on several dominant locations, and the spreading of wear scar often observed in the test conditions without the tapping treatments is eliminated. After the running-in process, the life-time of the tested silicon MEMS devices has been extended in dry nitrogen test environment from 1?min to more than 1?h.     

Microprocessor Control of Running-in of Plain Bearings

Correct running-in procedures have a major influence on the subsequent life and performance of a plain bearing. With very large bearings, the process can be both time-consuming and expensive.

It is necessary to control the running-in conditions very carefully, since too thick a lubricant film, will retard the running-in, while too little lubrication will lead to overheating and possible damage or even seizure. Since the surface topography is changing continuously during running-in, the optimum lubrication condition also changes.

This paper describes a new bearing rig in which running-in parameters are monitored and fed to a microprocessor which, in turn, controls the loading and speed conditions. The objective is to obtain correct running-in, in the minimum possible time.