汽车用薄板表面的空间特征的研究

提出了三个空间参数来表征汽车用薄板表面的频率分量的构成、纹理方向性和峰密度等空间特征。利用触针表面形貌仪和数据采集系统对不同类型薄板的三维形貌进行了测量,计算了各个薄板的空间参数值,对各薄板表面形貌的空间特征进行了分析。     

Applications of Hurst orientation transform to the characterization of surface anisotropy

Fractal-based methods have been used in surface characterization with increasing success over the past years. These methods have been employed to characterize isotropic surfaces but, as yet, little quantitative consideration has been given to the characterization of anisotropic surfaces. In this work, the Hurst orientation transform (HOT) is used to characterize the surface anisotropy and directionality. The calculation of the HOT involves searching all pairs of pixels in a circular region to build a table of maximum differences. From this table, the Hurst coefficients are calculated in many directions and plotted as a function of orientation to reveal surface anisotropy. In this work, two new surface texture parameters, i.e. texture aspect ratio and texture direction, obtained from rose plots of the Hurst coefficients were used in the characterization of surface anisotropy and directionality. Applications of the HOT method to stereo and interferometric images of wear particles and X-ray images of healthy and osteoarthritic joints are also demonstrated.     

IF钢板锌镀前后热电势的测定

研究了冷轧IF钢板镀锌前后的热电势（TEP）特性。试验结果表明：镀锌退火后,钢板基体发生再结晶导致TEP值升高,而镀层的形成导致TEP值下降。基体的再结晶起主导作用,并且,TEP值存在各向异性,这与钢板的织构有关。     

拉深模激光毛化表面的磨损性能研究

为提高拉深模的磨损性能和使用寿命,利用激光毛化技术在模具钢试样表面分别加工出不同直径和间距的微单元体。对比研究毛化表面试样和非毛化表面试样的磨损性能,结果表明,毛化试样表面耐磨性均优于非毛化表面试样。通过激光毛化可提高拉深模寿命,改善板料成形时的流动性。     

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.     

多尺度表面形貌的功能评定与控制

多尺度表面中,不同加工过程形成的纹理成分具有不同的粗糙度尺度和性能。多尺度表面形貌的功能评定,关键是识别不同的纹理成分,描述其功能属性。基于概率曲线和支承率曲线,提出一种多尺度表面形貌的功能评定方法,并研究了表面形貌的加工控制问题。对平台珩磨缸套表面的功能评定与控制研究表明,这种多尺度表面的功能评定方法是可行的。以ISO13565-3粗糙度参数为纽带,建立联系表面功能与加工工艺的经验模型,可以实现面向功能的表面质量控制。     

Impact of Wire-EDM on Tribological Characteristics of ZrO<Subscript>2</Subscript>-based Composites in Dry Sliding Contact with WC–Co-Cemented Carbide

In the present investigation, experiments were conducted by unidirectional sliding of pins made of FCC metals (Pb, Al, and Cu) with significantly different hardness values against the steel plates of various surface textures and roughness using an inclined pin-on-plate sliding apparatus in ambient conditions under both the dry and lubricated conditions. For a given material pair, it was observed that transfer layer formation and the coefficient of friction along with its two components, namely adhesion and plowing, are controlled by the surface texture of the harder mating surfaces and are less dependent of surface roughness (R _a) of the harder mating surfaces. The effect of surface texture on the friction was attributed to the variation of the plowing component of friction for different surfaces. It was also observed that the variation of plowing friction as a function of hardness depends on surface textures. More specifically, the plowing friction varies with hardness of the soft materials for a given type of surface texture and it is independent of hardness of soft materials for other type of surface texture. These variations could be attributed to the extent of plane strain conditions taking place at the asperity level during sliding. It was also observed that among the surface roughness parameters, the mean slope of the profile, Δ _a, correlated best with the friction. Furthermore, dimensionless quantifiable roughness parameters were formulated to describe the degree of plowing taking place at the asperity level.     

Calculations of earing in deep drawing for BCC metal sheets using texture data

The present study aims to calculate the height at each peripheral position of a cup drawn from a polycrystalline BCC metal sheet using texture data. In an analytical treatment, the polycrystalline sheet is simplified by considering it to be an aggregate of many single crystals with various orientations. A three-dimensional crystalline orientation distribution function which is constructed from measured texture data is used as the volume fraction of a particular oriented crystal. The ear is calculated crystallographically by considering both restricted glide and pencil glide. In an experiment four kinds of steel sheets were used. An average texture over a thickness of the sheet was measured by the Schulz reflection method. The calculated ear based on the measured texture was compared with the experimental ear for each sheet. The results show that all principal features of the ear of the drawn cup are predicted satisfactorily by the calculation in which pencil glide is not taken into consideration.     

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。     

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.     

Correlations for roughness,slope and peak height for bead blasted surfaces

Surface texture plays an important role in understanding heat flow through the interface of the contacting surfaces. In a majority of experimental investigations, however, only the surface roughness is reported. Hence, it was found desirable to determine functional relationship between the rms roughness, slope and peak heights. This work reports the results of measurements of the topography of 79 rough surfaces. The materials were stainless steel, mild steel, aluminium and copper. The surfaces of the specimens were blasted with particles of different materials at a range of pressures. It was found that profile heights were generally Gaussian. Simple correlations between measured parameters were developed. Analysis was also conducted based on the effect of different cut-off lengths. It was confirmed that roughness parameters are not intrinsic properties of the surface, but depend on the cut-off length.     

Drawability assessment of BCC steel sheet by using elastic/crystalline viscoplastic finite element analyses

Elastic/crystalline viscoplastic finite element (FE) analyses were carried out to asses the drawability of three kinds of BCC steel sheets, such as mild steel, dual-phase steel and high-strength steel, in the cylindrical cup deep drawing processes. In this study, the crystal orientations were obtained by X-ray diffraction and orientation distribution function (ODF) analyses. The measured ODF results have revealed clearly different textures of sheets, featured by orientation fibers, skeleton lines and selected orientations in Euler angle coordinate space, which can be related to the plastic anisotropy. An orientation probability assignment method, which can be categorized as an inhomogenized material modeling, was used in this FE modeling. The orientations were determined from the measured ODF and assigned to FE integration points one by one. Numbers of integration points, which represent crystallites and can rotate individually, are employed to represent textures of the sheet metals for taking account of the initial and evolutional plastic anisotropy without introducing Taylor or Sachs homogenization assumption. The FE analyses showed how the fiber textures affect the strain localization and earing in the deep drawing operation. It was confirmed by comparison with experimental results that this FE code could predict the extreme strain localization and earing with good accuracy and assess the sheet drawability.     

Anisotropic Friction of the Ventral Scales in the Snake Lampropeltis getula californiae

Since the ventral body side of snakes is in almost continuous contact with the substrate during undulating locomotion, their skin is presumably adapted to generate high friction for propulsion and low friction to slide along the substrate. In this study, the microstructure of ventral scales was analyzed using scanning electron microscopy, atomic force microscope and confocal laser scanning microscopy. Dynamic friction was investigated by a microtribometer. The ventral scales demonstrated anisotropic frictional properties. To analyze the role of the stiffness of underlying layers on the frictional anisotropy, two different types of scale cushioning (hard and soft) were tested. To estimate frictional forces of the skin surface on rough substrates, additional measurements with a rough surface were performed. Frictional anisotropy for both types of scale cushioning and rough surfaces was revealed. However, for both types of surface roughness, the anisotropy was stronger expressed in the soft-cushioned sample. This effect could be caused by (1) the stronger interaction of the microstructure with the substrate in soft-cushioned samples due to larger real contact area with the substrate and (2) the composite character of the skin of this snake species with embedded, highly ordered fiber-like structures, which may cause anisotropy in material properties.     

Influence of Steel Type on the Propensity for Tribochemical Wear in Boundary Lubrication with a Wind Turbine Gear Oil

Tribochemical wear may occur at the interface between a surface and a lubricant as a result of chemical and mechanical interactions in a tribological contact. Understanding the onset of tribochemical wear damage on component surfaces requires the use of high resolution techniques such as transmission electron microscopy (TEM). In this study, two steel types, case carburized AISI 3310 and through-hardened AISI 52100, were wear tested using a ball-on-disk rolling/sliding contact tribometer in fully formulated commercial wind turbine gearbox oil under boundary lubrication conditions with 10% slip. With the exception of steel type, all other test conditions were held constant. Conventional tribofilm analysis in the wear tracks was performed using X-ray photoelectron spectroscopy, and no significant composition differences were detected in the tribofilms for the different steel disk types. However, TEM analysis revealed significant tribochemical wear differences between the two steel types at multiple length scales, from the near-surface material microstructure (depth < 500 nm) to the tribofilm nanostructure. Nanometer-scale interfacial cracking and surface particle detachment was observed for the AISI 52100 case, whereas the tribofilm/substrate interface was abrupt and undamaged for the AISI 3310 case. Differences in tribofilm structure, including the location and orientation of MoS₂ single sheet inclusions, were observed as a function of steel type as well. It is suggested that the tribochemical wear modes observed in these experiments may be origins of macroscopic surface-initiated damage such as micropitting in bearings and gears.     

Studies on friction and transfer layer: role of surface texture

Friction influences the nature of transfer layer formed at the interface between tool and metal during sliding. In the present investigation, experiments were conducted using “Inclined Scratch Tester” to understand the effect of surface texture of hard surfaces on coefficient of friction and transfer layer formation. EN8 steel flats were ground to attain surfaces of different textures with different roughness. Then super purity aluminium pins were scratched against the prepared steel flats. Scanning electron micrographs of the contact surfaces of pins and flats were used to reveal the morphology of transfer layer. It was observed that the coefficient of friction and the formation of transfer layer depend primarily on the texture of hard surfaces, but independent of surface roughness of hard surfaces. It was observed that on surfaces that promote plane strain conditions near the surface, the transfer of material takes place due to the plowing action of the asperities. But, on a surface that promotes plane stress conditions the transfer layer was more due to the adhesion component of friction. It was observed that the adhesion component increases for surfaces that have random texture but was constant for the other surfaces.     

On the influence of imaging conditions and algorithms on the quantification of surface topography

The influence of the microscopical magnification resulting in different voxel size and shape and of the algorithm on parameters used for the quantification of the surface topography is studied using topographical images obtained by confocal laser scanning microscopy. Fracture surfaces and wire‐eroded surfaces of steel were used as samples. The values obtained for the global topometry parameters normalized surface area, mean profile segment length and fractal dimension depend with different degrees on the microscopic magnification and on the algorithm used to compute these values. The topometry values can only be used to establish correlations between the topography and materials properties and for the modelling of surface generating processes if the imaging and computing details are given.     

Methods of measuring and characterising the surface geometry of road stones

Methods of measuring and characterising random rough surfaces have always been of interest in the field of engineering. Measurement and analysis of finer scales of texture of a surface are now mainly effected by the use of a stylus instrument.Because of the finite radius of the tip of the stylus, this instrument cannot sense all the scales of texture on a surface. Evaluation of scales of texture finer than that sensed by the stylus instrument is of interest in many fields of engineering and in the prediction of hysteretic friction and of abrasion of rubber in particular. Two new methods which meet this demand to a great extent are described and their application is illustrated by actual measurements on stone surfaces. A scanning electron microscope is used in one method and an optical microscope in the other. Numerical methods of solution using electronic computers are adopted for the evaluation of texture parameters in both methods.     

人工髋关节织构化表面摩擦学性能研究

为研究微织构形状对人工髋关节表面摩擦特性的影响,在人工髋关节表面分别设计仿生菱形织构、圆柱形织构和圆环形织构,以雷诺方程为理论研究基础建立流体动压润滑模型,用ANSYS Fluent进行数值模拟,得到微织构表面润滑油膜的平均承载力和摩擦因数,并比较不同织构形状的摩擦学性能。结果表明：在所选织构参数、工况参数范围内,平均承载力随着面积率增大以及滑动速度的提高均呈现上升趋势,在面积率为25%、滑动速度为0.3 m/s时达到最大;摩擦因数随着织构面积率的增大而呈下降趋势,在面积率25%达到最小值,摩擦因数与滑动速度的关系则因织构形状的不同存在一定的差异;研究的3种形状微织构中,仿生菱形织构的摩擦学性能最佳。因此合理选择织构形状可以减少人工髋关节摩擦副表面间的磨损。     

三维粗糙表面的计算机生成及其纹理控制

工程实际中,大部分机械加工后的表面都存在一定的纹理,纹理作为表面的一种空间特征,无法用单一的表面形貌参数来描述其各向异性特征。利用基于AR模型的二维数字滤波技术,通过计算机模拟生成具有指定自相关函数的粗糙表面;通过控制自相关函数来控制纹理,获得纹理的本质特征,在此基础上提出了一种能有效模拟所需表面纹理的自相关函数。结果表明:数字滤波的方法能比较准确地生成具有规定自相关函数的表面;表面纹理与自相关函数的周期分量相关,可通过控制自相关函数的周期特征来模拟具有周期性的加工表面纹理。最后通过与WYKO实测的表面对比以及由实测表面来获得自相关函数的图像对比,证实方法的有效性。