High speed measurement of engineering surfaces

This paper considers the case for on line gaging of surface texture. Some systems for the logical implementation of gaging and the traceability of the necessary standards are discussed.The introduction of some well known statistical functions such as auto and cross correlation, via optical techniques are cited, along with methods for using coherent scattering (speckle) and specular reflection to gage finish.The use of unthinking routines based upon simple logic and patterned on the compound eye of lower crustations can give the speed along with low cost, that may be required in the production environments of the future.     

Fractal characterization of wear-erosion surfaces

Wear erosion is a complex phenomenon resulting in highly distorted and deformed surface morphologies. Most wear surface features have been described only qualitatively. In this study wear surfaces features were quantified using fractal analysis. The ability to assign numerical values to wear-erosion surfaces makes possible mathematical expressions that will enable wear mechanisms to be predicted and understood. Surface characterization came from wear-erosion experiments that included varying the erosive materials, the impact velocity, and the impact angle. Seven fractal analytical techniques were applied to micrograph images of wear-erosion surfaces. Fourier analysis was the most promising. Fractal values obtained were consistent with visual observations and provided a unique wear-erosion parameter unrelated to wear rate.     

The perturbation dimension for describing rough surfaces

We define global and local “perturbations” of roughness profiles, considered as rectifiable or non rectifiable curves. The method consists in measuring classical roughness parameters in τ — windows of various sizes. When τ tends to zero a characteristic scaling exponent is evaluated. This exponent is related to the “perturbation dimension” d. In rectifiable cases d is an integer. Otherwise, d is a real number. As a practical application, we characterize the roughness evolution of a shot-blasted surface as a function of the abrasive particule size.     

Multi-scale analysis of engineering surfaces

Conventional surface characterization techniques involving random process analysis are limited in characterizing multi-scale surface features relevant to manufacturing processes and functions. This paper introduces a novel technique for multi-scale characterization of engineering surfaces by applying wavelet transform. The main advantages of wavelet transform over other existing signal processing techniques are its space-frequency localization and multi-scale view of the components of a signal. Utilizing these properties of wavelet transform, we can effectively apply multi-channel filter banks to the surface data and link the manufacturing and functional aspects of a surface with its multi-scale features. Surfaces produced by typical manufacturing processes are analyzed using wavelet transform, and the usefulness of wavelet transform in the multi-scale analysis of engineering surfaces is demonstrated.     

大锻件尺寸在线测量技术的研究

大锻件尺寸测量是大型锻件生产中的重要环节。大锻件在锻造过程中的精确测量对提高锻件的质量和加工效率以及材料的利用率具有十分重要的意义。传统的接触式测量技术已经满足不了现代工业化的需求,而非接触式测量技术以其快速、准确的特点得到了迅速的发展。介绍了机械式测量方法、基于激光的测量方法、基于CCD的视觉测量方法以及基于结构光的视觉测量方法,分析了各种方法的适用性和优缺点,并提出了一种基于线结构光的CCD相机扫描法。最后对高温大锻件尺寸在线测量的现状进行了总结。     

Deformations of engineering surfaces under static loads

A computer-aided-system has been developed to provide (i) 3-D assessments of engineering surfaces; (ii) quantifications of surface degradations due to wear and deformation processes; and (iii) predictions of the true area of contact formed between two initially-isothermal, circular cross-sectional surfaces of a soft rough material (duralumin) and a relatively-harder smooth material (titanium) pressed together by a mechanical load. This system is based on a stylus profile-tracing instrument and incorporates an automatically-controlled parallel-profile digitising stage.     

Accuracy of replica materials when measuring engineering surfaces

This paper presents a comprehensive study of three different materials used for surface roughness replication on five different types of machined surfaces. Steel sheets (electron beam texturing and shot blasted texturing), a cylinder liner, a crankshaft and a face-ground surface. The three different replica materials used were Araldite, Microset and Technovit. The surfaces were measured with the non-contact WYKO interference instrument, zoomed to relocate the same area on the original and on the replicas. Finally, three-dimensional surface parameters were calculated to compare each replica with the original surface.The results show that all materials are possible to use in order to measure and calculate three-dimensional surface parameters, but they have some peculiarities. The three replicas all show good accuracy on all surfaces, with deviations <10%, except for the crankshaft. Only Araldite and Technovit occasionally show S_z values that are >10% too high due to a small number of pores in these materials. Replicas in the Microset material in general show somewhat lower parameter values than the original surface. All replicas showed some problems on the fine-ground crankshaft with an enlargement of the fine structure, resulting in parameters ca 20% too large. The deviation of surface parameters on repeated measuring on replicas is considerably larger than on repeated measuring of the original surfaces.     

Texture classification of engineering surfaces with nanoscale roughness

The spatial structure of the surface layer, or texture is important for surface topography characterization. In many respects a texture determines contact behavior of the rough surfaces. Despite increasing role of the precision mechanics, the texture of engineering surfaces have not been adequately investigated. In this paper pattern recognition theory is introduced to perform surface textures classification. The height-coded images obtained by atomic force microscopy were used as initial data. The images represent the surface textures of various materials formed by various processes. We take the following procedure for the texture classification. First, the texture was characterized by a matrix of co-occurrence of image contrast. Next, the matrix is transformed into feature vector by the Karhunen-Loeve transformation. The feature vector was considered as coordinates of a point in the multidimensional feature space. The location of the point depends on the peculiarities of the surface texture. The set of the points form clusters that correspond to different classes of textures. The mutual arrangement of the points and structure of the clusters were analyzed by the multidimensional scaling procedure. It was founded that there is at least four classes of surface relives. The first three of them related to the properties of surface material and the last to the process of growth and crystallization on the interface of different materials.     

硼酸铝晶须增强6061铝合金复合材料的断口分形分析(英文)

硼酸铝晶须增强6061铝合金基复合材料中的界面反应影响其断口分形维数。该复合材料由压力铸造法制备,采用垂直剖面法分析拉伸断裂断口。当量尺度分别取3-15μm以及1-5μm时,可以在断口上发现分形现象。当量尺度在3-15μm的分形域,其分形维数与材料抗拉强度显著正相关。实验结果表明,随热处理时间的延长,界面反应产物的分布与状态可以改变材料的微观断裂模式,进而影响断口的粗糙度和分形维数,同时决定材料的抗拉强度。而当量尺度为3-15μm的分形域,其分形维数受热处理程度的影响不很显著。     

Autonomous form measurement on machining centers for free-form surfaces

This research aims at developing a measurement technique on machining centers for 3D free-form contours. An autonomous measuring principle is proposed and a prototype measuring device applicable to a machining center has been produced. In the measuring device, a laser displacement detector in a narrow range, which directly detects the distance from a point on the measured surface to the reference position of the detector output, is put together with the movable part of a linear encoder on the nut of a ball screw. A stepping motor controls the laser detector position to keep the output at the central value of the detector measuring range by driving the ball screw. Both the motor and the fixed part of the linear encoder are placed on the device base. The linear encoder detects the moving displacement of the screw nut, i.e. the position change of the laser detector. By installing the base on the spindle of a machining center and moving the table along a plane perpendicular to the spindle, the laser detector can automatically follow the contour of a work piece set on the table and measure its form along a scanning line, simultaneously. The displacement of a measured point relative to the reference position of the linear encoder output on the spindle side is just equal to the sum of the outputs of the two sensors, i.e. the laser detector and the linear encoder. Moreover, a simple experimental approach to identifying the sensing direction errors for an assembled measuring device is developed. The results of some experiments are also shown, which sufficiently demonstrate the effectiveness of the proposed inspection method and error identification approach.     

The measurement and analysis of the three-dimensional form of curved surfaces

In an attempt to reduce manufacturing costs, contact lenses are manufactured using a cast moulding technique. If quality is to be maintained, it is essential that the mould components are manufactured to very high standards, with particular emphasis being placed on the curvature of the optical surfaces. If these surfaces are to be: accurately measured and described, then they must be considered in three dimensions. Several different :measurement instruments have been considered for this purpose, and three-dimensional numerical algorithms developed for assessment of the data from these instruments.     

标志点拼接技术在大型薄壁件型面非接触测量中的应用

随着测量技术的发展 ,大型塑性成形零件的型面检测方法有了较大的改善。本文首先介绍了三维拼接技术的基本原理 ,阐述了手工设定拼接标志点的拼接算法的实现过程。最后给出了该方法在大型蒙皮零件型面测量中的应用实例和拼接效果 ,为控制零件成形精度提供了可靠的检测手段     

Surface roughness measurement on machined surfaces using angular speckle correlation

Surface roughness is of great importance in fields, such as tribology, semiconductor technology and medicine. Stylus techniques, in which a stylus is drawn along the surface and the vertical movement of the stylus is recorded, have been used traditionally in measuring surface roughness. Non-contact methods, such as optical ones, have the advantage that they can be used for the in-process measurement of surface roughness. In this paper, results of the measurement of surface roughness using angular speckle-correlation on machined surfaces are presented. Surfaces of approximately 1.6 < R_a < 6.3 μm have been measured, the surfaces being classified in the same manner as when using a stylus instrument. ASC is a technique that also allows in-process measurement of the roughness of surfaces on machined surfaces. A new technique to achieve increased repeatability by using an angle detection unit is also presented in this paper.     

Hardware variability in the three-dimensional measurement of autobody steel panel surfaces

Automotive panel manufacture is an important industrial activity. Research in this area has recently been assisted by an European Community funded research programme on three-dimensional characterisation of steel sheet. This paper describes the results of the first part of the programme in which the emphasis is on a Round Robin Test of the partners measuring equipment. Software was identified as being one of the major causes of variability. It is concluded that standard and stable algorithms are a necessity to ensure reliable interchange of data.     

基于激光测量的自由曲面零件逆向工程的实现

介绍了非接触式激光测量系统的软硬件组成，分析了未知自由曲面零件的测量规划和测量数据处理方法，并通过一个鼠标模型的测量和重建，验证了该系统的可行性，为自由曲面零件逆向工程的实现奠定了基础。     

evaluation of engineering surfaces using a combined fractal modeling and wavelet analysis method

A new approach based on the combination of wavelet and fractal theories is proposed. The purpose is to provide a mechanism to evaluate the characteristics of engineering surfaces more accurately and comprehensively. The wavelet transformation models and the fractal representation of engineering surfaces are presented and the combination of the wavelet models and the fractal representation is investigated. Using the proposed approach, the experimental samples of the workpiece surface obtained through grinding are examined. The results demonstrate that the proposed approach is accurate and comprehensive.     

Profile error compensation in ultra-precision grinding of aspheric surfaces with on-machine measurement

A compensation approach based on the on-machine measurement was developed for the grinding of tungsten carbide aspheric moulds. In this approach, the on-machine measurement was employed to eliminate the profile error caused by the re-installation of the workpiece. A new method was proposed to reconstruct the actual ground profile based on the measured profile data. The overall profile error after grinding was obtained by subtracting the target profile from the actual ground profile along normal direction and was then used to generate a new tool path for compensation grinding. The experimental results showed that after three compensation grinding cycles the aspheric surface had a profile accuracy of 177 nm (in PV) with a roughness of 1.7 nm (in R_a). The on-machine measurement was in excellent agreement with the off-machine measurement by commercially available profilometers.