钢铜摩擦副摩擦磨损特性的试验研究

本文试验分析了ＺＱＡ１９－４和ＺＱＺｎ６－６－３两种铜合金材料在不同的表面粗糙度下对摩擦系数和出口区油温的影响，以及改变载荷和相对滑动速度时，摩擦系数的变化状况。结果表明；铜合金成分不同时具有不同的硬度。     

滑动摩擦副抗咬死性能的试验研究

咬死是高速,重载滑动摩擦副常见的失效形式之一。在ＭＨＫ－５００型块磨损试验机上对４５＾＃淬火,４５＾＃调质,ＧＣｒ１５,ＺＱＡＬ９－４材质组成的滑动摩擦副进行了抗咬死性能试验研究。试验结果表明;构成摩擦副材料的粗糙度,相对滑动速度,不同材质摩擦副对摩擦副抗咬死能力有一定的影响,改变摩擦副材质性能提高摩擦副抗咬死能力;     

一种板料成形摩擦系数的反求技术

基于摩擦边界条件对板料成形过程及其有限元仿真的巨大影响,利用材料拉伸试验,给出了一种板料成形摩擦系数的反求技术。该技术结合数值模拟、实验技术以及遗传算法中的小种群算法,通过反求原理,计算得到在成形过程中利用实验难以测得的摩擦系数。最后通过同种材料在两种不同摩擦条件下的试验,分别反求出该两种条件下的摩擦系数,分析了这种方法的可行性。     

聚氨酯弹性体摩擦衬垫材料的摩擦特性研究

本文研究了聚氨酯弹性体摩擦衬垫材料的摩擦特性,发现聚氨酯弹性体材料的动摩擦系数是和滑动速度有关的,在0．0l-0．4mm／s的速度范围内,速度提高摩擦系数上升,在更高的速度下摩擦系数还会下降。聚氨酯弹性体材料的静摩擦系数是比较难以确定的,本文建议把滑动量较小而滑动速度又很低的这一时期的摩擦称为“初期摩擦”,它是界于静摩擦与动摩擦之间的一种特殊的摩擦状态。文中还分析了粘着摩擦机理,提出了接点化学粘接机理。并根据这种机理对实验结果进行了分析和讨论。     

Influence of Lubricant Additive and Surface Texture on the Sliding Friction Characteristics of Steel under Varying Speeds Ranging from Ultralow to Moderate

A newly developed tribometer that undergoes significant changes in sliding speed, ranging from ultralow (5 μm/s) to moderate (17 cm/s), was used to study the lubricated friction characteristic of steel. In this study, the friction characteristics of stearic acid-formulated oil were studied to clarify the effects of surface roughness or surface roughness texture on friction. Several kinds of specimens having isotropic and anisotropic surface roughness with different textures were used. For an isotropic surface, a rougher surface resulted in low friction under low-speed conditions. The same surface produced high friction under high-speed conditions, where macroscopic hydrodynamic action was predominant. Remarkably less friction was observed in the transverse than in the longitudinal direction when the specimen had anisotropic roughness. This difference was particularly notable under ultra-low-speed conditions. Two other parameters of skewness and kurtosis of roughness distributions show that low friction was obtained when surface roughness distribution approached normal. It appears that the low friction observed with a rough surface or a transverse roughness direction could be explained by the microscopic hydrodynamic action of fluid together with the lubricity of the adsorbed molecular layer.     

摩擦力-相对滑动速度关系的实验研究

对金属往复滑动摩擦力-相对滑动速度的关系进行了试验研究，通过设计相对滑动速度曲线实现了无摩擦振动工况下的摩擦力-相对滑动速度关系的测量。文中还对摩擦振动工况下的摩擦力的测量作了探讨。本文的试验数据可作为摩擦振动和摩擦噪声理论研究的基础数据。     

Study of Friction and Transfer Layer Formation in Copper-Steel Tribo-System: Role of Surface Texture and Roughness Parameters

In the present investigation, experiments were conducted on a tribological couple—copper pin against steel plate—using an inclined pin-on-plate sliding tester to understand the role of surface texture and roughness parameters of the plate on the coefficient friction and transfer layer formation. Two surface characteristics of the steel plates—roughness and texture–were varied in the tests. It was observed that the transfer layer formation and the coefficient of friction along with its two components, namely, the adhesion and plowing, are controlled by the surface texture of the plate. The plowing component of friction was highest for the surface texture that promotes plane strain conditions while it was lowest for the texture that favors plane stress conditions at the interface. Dimensionless quantifiable roughness parameters were formulated to describe the degree of plowing and hence the plane strain/stress type deformations taking place at the asperity level.     

A Refined Friction Modeling for Lubricated Metal Forming Process

In spite of the existence of a well-developed realistic friction model, it has only been applied to the simple geometric problems, such as the axisymmetric and plane strain conditions, where the formulations of lubricant transport can be decomposed into two characteristic equations. Accordingly, a unified procedure of combining the current lubrication/friction model and finite element code of metal forming has been developed in this article for either steady or unsteady three-dimensional process including both axisymmetric and plane strain cases. In the part of the lubrication analysis, a finite element method is derived for the average Reynolds equation that is appropriated for 3-D metal forming process, and regardless of whether the tooling/workpiece surfaces are in contact or not. With regard to the theory of asperity contact, in addition to the well-known smoothing and roughening effects, significant deformation of asperities could be caused by the elastic microwedges on the tool surface. The availability of the new friction model was proved by a published problem and an axisymmetric stretch forming process was therefore adopted as a benchmark. Numerical results showed that the present analysis provides a good agreement with the measured strain distributions.     

外加电场主动控制摩擦系数的试验研究

外加电场可以显著改变铁磁流体的摩擦系数,本文利用销一盘试验机进行了研究,结果表明,加电场作用前后ＢＨ－１铁磁液体的磨擦系数相对变化与电流以强度关系密切,而对法向载荷、线速度和添加剂含量的变化不敏感。在正反电场的作用下,摩擦系数的最大变化率可达到３５％,而且变化过程具有可逆性。在研究电场对铁磁流体摩擦系数变化的影响的基础上,探讨了电流产生的静电场和磁场对摩擦系数的作用机下。     

干摩擦条件下45号钢渗硫层的摩擦磨损性能试验研究

采用低温离子渗硫技术，在不同预先热处理的45号钢表面形成渗硫层，在干摩擦条件下，对渗硫试件和非渗硫试件进行了摩擦磨损试验，试验表明：经低温离子渗硫处理的试件，具有较好的减摩和耐磨作用。     

Experimental Investigation of Friction Effects Enhanced by Tool Geometry and Forming Method on Plane Strain Sheet Metal Forming

An experimental study on friction was conducted on aluminum and steel sheets for automotive applications. Cold-rolled mild and high strength steel, electrogalvanized steel and aluminum grades Al6111T4 and Al 2008T4 were tested under various levels of bending under tension, plain strain forming mode. The friction and forming severity of the tests were promoted through the use of a set of tools of decreasing radii sizes. The test methods includes flat platens, draw bead simulation, 90-degree bending under tension and tools with rectangular geometry. A systematic pattern of frictional behavior, common to all tests was observed. An initial spike, associated to static friction, was followed by a more stable plateau. The effects of the static friction on the forward flow were studied in function of parameters such as the testing method, the tool radii, the testing speed, etc. The results showed that the static friction may be increased by the forming method, and its effects on the forward flow varied significantly depending on the material and lubrication. Based on the results of this study, general forming practices for these materials were recommended.     

Analysis of Strain Rates and Microstructural Evaluation during Metal Forming: Role of Surface Texture and Friction

The surface texture of a die plays an important role in friction during metal forming. In the present study, unidirectional and random surface finishes were produced on hardened steel plate surfaces. To understand the influence of surface texture on friction, experiments were conducted using Al-Mg alloy pins that slid against steel plates of different surface textures. In the sliding experiments, a high coefficient of friction was observed when the pins slid perpendicular to the unidirectional grinding marks and low friction occurred when the pins slid on the random surfaces. Finite element simulations were performed using the measured friction values to understand the stress and strain evolutions in the deforming material using dies with various friction. The numerical results showed that the states of stress and strain rates are strongly influenced by the friction at the interface and hence would influence the final material microstructure. To substantiate the numerical results, laboratory compression tests were conducted. Different surface textures were obtained in order to experience different friction values at different locations. A large variation in the microstructure at these locations was observed during experiments, verifying that surface texture and die friction significantly influence fundamental material formation behavior.     

Surface lay effect on rough friction in roller contact

Surface lay describes the direction of the predominant surface pattern. A properly designed surface texture configuration has been recognised as a vital issue affecting lubrication and sliding in machinery applications in the literature. Gaining understanding of this tribological phenomenon is no doubt beneficial in facilitating the production of more efficient machine parts and thus reduces production cost. This paper describes an experimental method to investigate the effect of surface lay on lubricated rolling/sliding of ground roller surfaces. By using the rough friction test rig, different surface lay contacts can be simulated and the friction can be measured. Friction behaviour was interpreted in terms of Stribeck curves (friction coefficient as the function of Hersey parameter [ην/p]). Results show that an optimal contact lay angle that provides a minimum friction value is achievable through rig testing. The relative sliding speed direction has a symmetrical effect on friction at the same lay orientation; for sliding speed angles less than about 80°, the larger the angle, the lower the friction, and vice versa.     

The Scale Effect of Roughness on Hydrodynamic Contact Friction

Multistage abrasive finishing processes (grinding, polishing, honing, etc.) are commonly used to produce the geometrical properties of a surface to meet its technical functionalities in the operating characteristics of contacting parts in friction, relating to their durability and reliability (running-in performance, wear resistance, load-carrying capacity, etc.). Coarse abrasive grits followed progressively finer ones are used, which leads to a multiscale stratified surface texture.

In this article, a numerical model of elastohydrodynamic (EHD) contact coupled to a multiscale surface texture model was developed that allows tracking the scale effect of surface features and their interactions on friction performance and lubricant flow under hydrodynamic lubrication conditions. Because the simulation model has as an input the surface topography and to overcome the variability in surface finish formation, textured surfaces at different stages of the finishing process were simulated (virtual texturing method). Surface topography can be decomposed into two principal components: superficial roughness and valleys. Superficial roughness was modeled using a fractal model and a scaling factor was introduced to model valley patterns. The results show the relationship between friction and surface scales.     

45^#钢滑动摩擦副咬死温度变化特征的试验研究

温度变化是摩擦副胶合前期重要特征之一。在ＭＨＫ－５００型块式磨损试验上，采用热电偶测温技术，对４５＾＃淬火钢和钢试环、试声滑动摩擦副咬死过程的温度变化特征进行了试验研究。试验结果表明：胶合瞬间，摩擦副表面温度发生了突变，胶合发生后，摩擦副是否发生咬死受材料高温下机械特性以及润滑方式等因素的影响。磨擦副表面微凸峰之间以及润滑油中磨屑与摩擦副表面间的微切削作用是导致磨擦副表面温度突变的原因之一。     

研究拉深用润滑剂的摩擦特性

拉深用润滑剂在使用中的摩擦特性与拉深工艺之间的关系目前研究的还比较少,本文针对这一内容进行研究.实验采用拉深工艺模拟试验机作为实验手段,研究油基和水基润滑剂在给定不同压边力值条件下的润滑性能、以及坯料直径变化对润滑性能的影响.实验结果表明:(1)在拉深过程中,水基润滑剂存在一个最佳压边力范围,在这一范围内水基润滑剂具有比油基润滑剂摩擦系数小、拉深性能好的特点.当超过这一范围时,摩擦系数明显增大,拉深性能变差.(2)油基润滑剂基本不受压边力的影响.(3)拉深坯料直径的变化对油基和水基润滑剂的摩擦性能都基本无关系.(4)建立了水基润滑剂的摩擦系数与拉深压边力之间关系的实验方程.     

Effects of Friction on the Contact and Deformation Behavior in Sliding Asperity Contacts

Finite-element analyses are carried out to study the effects of friction on the contact and deformation behavior of sliding asperity contacts. In the analysis, on elastic-perfectly-plastic asperity is brought in contact with a rigid flat at a given normal approach. Two critical values of the normal approach are used to describe the asperity deformation. One is the approach corresponding to the point of initial plastic yielding, and the other at the point of full plastic flow. Additional variables used to characterize the deformation behavior include the shape and size of the plastic zone and the asperity contact size, pressure, and load capacity. Results from the finite-element analysis show that the two values of critical normal approach decrease significantly as the friction in the contact increases, particularly the approach that causes plastic flow of the asperity. The size of the plastically deformed zone is reduced by the friction when the contact becomes fully plastic. The reduction is very considerable with a high friction coefficient, and the plastic deformation is largely confined to a small thin surface layer. For a low friction coefficient, the contact size, pressure and load capacity of the asperity are not very sensitive to the friction coefficient. For a moderate friction coefficient, the contact pressure is reduced and the junction size increased; the load capacity of the asperity is not significantly affected due to the compensating effects of the pressure reduction and the junction growth. For a high friction coefficient, the pressure-junction compensation is not longer sufficient and the asperity load capacity is reduced. The degree of the friction effects on these contact variables depends on the applied force or the normal approach. Although the analyses are conducted using a line-contact model, the authors believe that the effects of friction in sliding asperity contacts of three-dimensional geometry are essentially the same and the same conclusions would have been reached. These results may provide some guidance to the modeling of rough surfaces in boundary lubrication, in which the asperity friction coefficient can be high and vary significantly both in time and from one micro-contact to another.     

孔光整加工表面粗糙度在线测量实验研究

针对液体磁性磨具光整加工孔时,无法对孔内壁表面质量进行在线检测的现状,提出利用声发射技术检测加工过程中摩擦声发射信号并进而在线预测孔壁粗糙度的方法。通过实验和分析验证了声发射(Acoustic Emission,简称AE)信号与试件表面粗糙度值有良好的对应关系,获取了与孔壁粗糙度值相对应的AE信号特征值,研究了某零件光整加工时AE信号的均方根值与表面粗糙度值变化情况的对应规律,为利用声发射技术进行孔表面光整加工的在线检测和相关设备的自动化控制提供了有益的参考。     

摩擦噪声发生过程中摩擦力变化的研究

在干摩擦条件下，摩擦噪声的发生与接触界面的摩擦有密切的关系。本文测量了摩擦噪声状态下的摩擦力，利用小波变换可以把信号分解成不同频率成份的特点，对摩擦力信号进行了小波分解，结果可以看出在同一个往复行程里从无摩擦噪声到发生摩擦噪声的过渡阶段摩擦力的变化。分析结果显示当摩擦噪声的强度比较弱时摩擦力的变化比较光滑，但当噪声强度比较大时，摩擦力有一个台阶状的变化。     

硬质合金与钢摩擦时金属元素迁移的研究

研究了硬质合金与钢摩擦时金属元素的迁移行为,试验结果表明,在摩擦中施加含三乙醇胺润滑剂和干摩擦相比较,钨,钛,铁等金属元素的迁移率明显降低,而钴元素的迁移率却变化很小,分析原因是由于三乙醇胺会使硬质合金中的钴元素浸出所致。