Dynamic modelling of the fidelity of random surface measurement by the stylus method

A numerical simulation has been used to systematically investigate the characteristics of a stylus surface profiling instrument. The model bridges together previously used concepts to incorporate both tip size and tip dynamics. The dynamics incorporate a tip flight phenomenon, inferring detachment from zero value of the reaction force and the trajectory from a free vibration solution to a second order system. Tip shape is handled by a rigid kinematic model. Following brief discussions of the modelling and the process for generating test profiles with defined correlation lengths, the influences of the inherent parameters of the stylus instrument and the testing method on the measurement fidelity are examined. The tip shape effect of the stylus instrument is also considered in the dynamic measurement. It is noted that the finite tip size can increase the critical scanning speed to avoid tip flight, but decreases the signal fidelity of the measurement due to the bridging effect.     

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。     

Simulation of textured surface topography during a low wear process

Wear experiments were conducted on a block-on ring tester. The stationary block made from cast iron of 50 HRC hardness was ground. The rotated ground ring was made from 42CrMo4 steel of 32 HRC hardness. The rings were modified by a burnishing technique in order to obtain surfaces with oil pockets. Oil pockets of spherical and of drop shape were tested. The correlation and regression analysis of parameters of textured surface topography was carried out. Two sets of surfaces were analysed: after machining and after “zero-wear”. As the result of analysis, minimum number of parameters describing this surface kind was obtained. A simple truncation model of the ring surface change was used. Worn surface topographies, after a low wear, were also modeled in a different way. An idea of the proposed method of surface topography modeling is imposition of random surface of Gaussian ordinate distribution on the base surface (after burnishing). The modeled surfaces were correctly matched to the measured surfaces in 90% of all analysed cases. Basing on the simulation, the local wear values during a low wear process were calculated and compared with experimental ones.     

Quantitative characterization of abrasive surfaces using a new profile measuring system

An on-line computer-controlled profilometer is described for quantitative characterization of extremely rough surfaces such as grinding wheels and coated abrasives. Conventional profilometers offer difficulty in the characterization of such surfaces because of the tendency of the stylus to become stuck in the crevices. In this present system, the stylus oscillates while the surface below moves incrementally so that the surface is stationary when contacted by the stylus. Both stylus and wheel motion are controlled by a digital computer. Measurements of surface elevation are input to the computer for digital processing and various surface characteristics are computed. The use of the system is illustrated by showing the effects of grit size on coated abrasive topography.     

Modelling and simulation of structure surface generation using computer controlled ultra-precision polishing

The applications of structured surfaces have been more widespread. However, research on the fabrication of these surfaces is still far from complete. The paper presents a theoretical and experimental investigation of the generation of structured surfaces by using Computer Controlled Ultra-precision Polishing (CCUP). A surface topography simulation model and hence a model-based simulation system for the modelling and simulation of the generation of structure surfaces by using CCUP have been established and verified through a series of simulation and practical polishing experiments. The results of experiments demonstrate the capability of the model-based simulation system in predicting the form error and the pattern of the 3D-texture generated by using CCUP.     

Realistic simulation of surface defects in five-axis milling using the measured geometry of the tool

Managing macro- and micro-geometry of surfaces during manufacturing processes is a key factor for their following uses. Indeed, micro-geometry and surface topography are directly linked to the performances of functions (contact, friction, lubrication, etc.) by texture parameters to ensure the desired local geometry. Common models for simulation of surface topography are based on ideal geometry of the machining tool and cannot represent surface defects. The actual prediction and simulation of defects are one step forward in a competitive context. In this paper, the realistic model proposed aims to simulate and predict as finely as possible local defects of machined surfaces taking into account the actual edge geometry of the cutting tool. The combined use of the machining kinematics and of the measured geometry of the cutting edges leads to the representation of the geometrical envelope of the surface using a Zbuffer technique. Simulation assessment is carried out by the analysis of 3D surface topography parameters such as surface complexity and relative area and by a comparison of simulation results to an experimental case of study.     

三维表面形貌的逾渗特性表征

为了建立表面形貌微观结构与其功能特性之间的关系,基于逾渗理论建立了表面形貌的逾渗模型,用逾渗概率、空体集团平均大小和空体集团分布系数对三维表面形貌的逾渗特性进行了量化表征。采用数字滤波技术生成具有给定自相关函数和纹理取向的数字化粗糙表面,分析了具有相同均方根粗糙度而结构不同的三维表面形貌的逾渗特性,给出了表面纹理方向参数和自相关长度对表面逾渗特性的影响,并借助部分三维形貌参数(ISO25178)建立了表面形貌与逾渗特性参数间的量化关系。结果表明:对于各向异性表面,沿横向搜索跨越空体集团,表面逾渗发生时的表面高度、逾渗阈值和逾渗体积均随着表面纹理方向参数的增大呈减小趋势,而空体集团分布系数呈增大趋势;沿纵向搜索时,其变化规律与横向相反。对于各向同性表面,逾渗发生时的表面高度和逾渗阈值随着表面自相关长度的增大呈先减小后小幅增大趋势,而逾渗体积和空体集团平均大小呈逐渐减小趋势。研究结果为面向功能的表面形貌设计提供了理论基础。     

Model for the prediction of 3D surface topography in 5-axis milling

The paper deals with the prediction of the 3D surface topography obtained in 5-axis milling in function of the machining conditions. For this purpose, a simulation model for the prediction of machined surface patterns is developed based on the well-known N-buffer method. As in sculptured surface machining the feed rates locally vary, the proposed model can be coupled to a feed-rate prediction model. Thanks to the simulation model of 3D surface topography, the influence of the machining strategy on resulting 3D surface patterns is analyzed through an experimental design. Results enhance the major influence of the tool inclination on 3D topography. Surface parameters used in the study are strongly affected by the variation of the yaw angle. The effect of the feed rate is also significant on amplitude parameters. Finally, the analysis brings out the interest of using surface parameters to characterize 3D surface topography obtained in 5-axis milling.     

静态接触中表面纹理对塑性变形界面微凸体平坦化的影响

试验研究了静态接触中表面纹理对塑性变形界面微凸体平坦化的影响。运用抛光技术制备了两种试件表面:单向纹理表面和各向同性表面。采用HDM-20端面摩擦试验机,分别在有、无润滑油条件下对试件进行了压缩试验。用JM-6200型光学显微镜观测试件表面形貌结构的变化;用Talysurf CCI Lite测量三维表面参数,并选取S_a、S_(al)、S_(tr)、S_(dr)和S_(dq)等参数来定量描述试件表面形貌结构的变化。结果表明,试件表面纹理对微凸体平坦化行为具有明显的影响,无润滑油时各向同性表面微凸体平坦化程度大于单向纹理表面,但有润滑油时刚好相反;表面纹理对微凸体平坦化的影响使得三维表面参数发生了规律性变化。基于机械流变模型的分析表明,封闭润滑油坑的出现导致了有润滑油时表面纹理影响微凸体平坦化行为。通过封闭润滑油坑特征的提取,验证了分析的正确性。     

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。     

Assessment of surface finish on bulk scattering materials: A comparison between optical laser stylus and mechanical stylus profilometers

The accuracy of autofocusing laser stylus measurement systems based on the compact disk pick-up technique has been discussed in recent years, in particular for surface roughness measurement in the submicron-micron range. In this article we present a thorough comparison between an optical laser stylus measurement system and a Talystep mechanical stylus profilometer. Sixteen surfaces having root mean square roughnesses from 0.002 μm to 3 μm for cut-off lengths <0.8 mm have been used in the study. Both bulk scattering (paper, white ceramic) and surface scattering (metal sheet) types of samples were included. Our study shows that the laser stylus exaggerates the surface profile, in particular on surfaces having laterally small but steep local slopes. For the paper surfaces the laser stylus data were on average off by a factor of two for a cut-off length of 0.68 mm.     

球头铣刀加工曲面微单元理论建模与实验验证

针对球头铣刀已加工表面特有的“小凹坑”微单元结构，结合表面形貌几何参数对应的数学关系，求解了微单元特征参数及特征线表达式；结合实验结果修正了微单元特征参数并验证了其准确性，进而建立了曲面微单元三维仿真形貌。研究结果表明：修正后曲面微单元宽度相对误差为1.88%，长度相对误差为7.60%，验证了所建理论模型的准确性。     

Effect of a skid on the accuracy of measuring surface roughness

The vertical movement of the skid caused by surface irregularities introduces some error into the measured value of surface roughness parameters. A theoretical and experimental investigation into the negative effect of the skid on measuring accuracy is reported.The effect of the skid for unidirectional surface roughness is greater than that for non-directional surface roughness. The effect increases with increase in the tip radius of the skid. The influence of the distance between the skid and the stylus on the effect of the skid is small and an electrical high pass filter reduces the effect.     

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.     

Research on rotary surface topography by orthogonal turn-milling

As a new technology in manufacturing, turn-milling broadens the application ranges of mechanical processing, wherein both cutting tool and workpiece are given a rotary motion simultaneously. The objective of the present work is to study workpiece surface topography during orthogonal turn-milling process. This study begins with two mathematical models, which describe theoretical surface roughness and topography of rotationally symmetrical workpiece. The models are built with the establishment of locus function according to orthogonal turn-milling principle. Then based on these models, the influence law of surface topography affected by various cutting parameters is found by some simulation methods. The law also matches with orthogonal turn-milling surface roughness and topography experiments. By analyzing the experimental results, some parameter selection criteria during orthogonal turn-milling processing are also proposed qualitatively and quantitatively. The comparison between the simulation and experimental results shows that a better surface quality and tiny oil storage structure can be obtained if the cutting parameters are chosen in reason. This conclusion provides a theoretical foundation and reference for the orthogonal turn-milling mechanism research.     

Scratch testing of WC/Co hardmetals

Two grades of WC/Co hardmetals, a fine-grained sample and coarse-grained sample, were tested using single and multiple scratch tests with a spherical diamond stylus. The variation in damage mechanism with increasing number of scratch repeats was analysed using SEM, FIB and 3D confocal microscopy. An interesting feature is the formation of a thin tribo-layer on the surface of the scratched region, which becomes more evident at increased scratch repeats. Variations in the coefficient of friction were attributed to changes in the topography of the stylus and formation of a tribo-layer on the scratched surface.     

Metrological feasibilities of CMM touch trigger probes. Part I: 3D theoretical model of probe pretravel

New 3D model of the inaccuracy of a touch trigger probe used to collect coordinates of a measured object by coordinate measuring machine (CMM) is proposed. The analysis is performed both for one and two stage types of probes. The influence of a stylus length and diameter, a spring force and direction of a contact point approach are taken into consideration. The effects of frictional interaction between the stylus ball and a measured surface are also taken into consideration. The theoretical analysis of a tough trigger probe hysteresis is presented. Finally a computer simulation of mathematical modeling in the XYZ space is shown.     

Modeling and evaluating of surface roughness prediction in micro-grinding on soda-lime glass considering tool characterization

The current research of micro-grinding mainly focuses on the optimal processing technology for different materials. However, the material removal mechanism in micro-grinding is the base of achieving high quality processing surface. Therefore, a novel method for predicting surface roughness in micro-grinding of hard brittle materials considering micro-grinding tool grains protrusion topography is proposed in this paper. The differences of material removal mechanism between convention grinding process and micro-grinding process are analyzed. Topography characterization has been done on micro-grinding tools which are fabricated by electroplating. Models of grain density generation and grain interval are built, and new predicting model of micro-grinding surface roughness is developed. In order to verify the precision and application effect of the surface roughness prediction model proposed, a micro-grinding orthogonally experiment on soda-lime glass is designed and conducted. A series of micro-machining surfaces which are 78 nm to 0.98 ~tm roughness of brittle material is achieved. It is found that experimental roughness results and the predicting roughness data have an evident coincidence, and the component variable of describing the size effects in predicting model is calculated to be 1.5x 107 by reverse method based on the experimental results. The proposed model builds a set of distribution to consider grains distribution densities in different protrusion heights. Finally, the characterization of micro-grinding tools which are used in the experiment has been done based on the distribution set. It is concluded that there is a significant coincidence between surface prediction data from the proposed model and measurements from experiment results. Therefore, the effectiveness of the model is demonstrated. This paper proposes a novel method for predicting surface roughness in micro-grinding of hard brittle materials considering micro-grinding tool grains protrusion topography, which would provide significant research theory and experimental reference of material removal mechanism in micro-grinding of soda-lime glass.     

Changes of Surface Topography during Wear for Surfaces with Different Height Distributions

Surface topography is one of the leading factors affecting wear processes. This study investigated topographical changes of mechanical components with non-Gaussian surfaces under sliding wear. The Johnson translatory system of distributions was applied to describe different surface height distributions. A wear model that has been experimentally confirmed for sliding wear was used to describe changes of surface heights. Based on different wear particle size distributions generated during wear, variations of surface height distribution were investigated. Relationships between topographical change and original surfaces were established. Finally, the results predicted were compared with the results using a truncation wear model