Surface Texture Measurement

12 Key excerpts on "Surface Texture Measurement"

• 

  eBook - PDF

  Fundamentals of Dimensional Metrology

  • Connie Dotson(Author)
  • 2015(Publication Date)
  • Cengage Learning EMEA

    (Publisher)

  364 13 LEARNING OBJECTIVES ● State the significance of surface metrology. ● Explain the essential differences between surface metrology and other forms of dimen-sional metrology. ● Describe the basis for the assessment of surface texture. ● Explain the role of standards for surface texture. SURFACE MEASUREMENT CHAPTER THIRTEEN working applications of surface metrology are more for the look and feel of a product—and manufacturers set their own nondimensional, empirical standards— there are important standards set for items that contain parts that are subject to loads, that move in relation to one another, and that fit closely together, even if they do not move. To meet performance requirements, the surfaces must be prepared for the job: for “rough” mecha-nisms with surfaces that have distinctive textures, the surfaces can be cast, forged, or rolled. For surfaces that contact other surfaces, they must be finished by machining or another process (see Figure 13–1). Machining, from rough planing and milling to fine diamond turning, creates textures that resemble one another—and look nothing at all like unmachined textures—but whose measurements vary greatly. We create the finest machined surfaces with abrading OVERVIEW Surface metrology, which includes the commonly rec-ognized elements finish and roundness, is an impor-tant consideration in manufacturing. As the speed of machines and an industry-wide need for better reli-ability and cost control increase, the need to control surface features increases logarithmically. Surface metrology requires a new fundamental principle. The other fundamentals we have studied concern the relationship between a feature of a part or assembly and some other feature or the conceptual design. In contrast, surface metrology examines the deviation between one point (or points) on a surface and another point (other points) on the same surface.

  Sign up to read

  Learn more about book
• 

  eBook - PDF

  Manufacturing Surface Technology

  Surface Integrity and Functional Performance

  • Brian Griffiths(Author)
  • 2001(Publication Date)
  • Butterworth-Heinemann

    (Publisher)

  3 Surface Finish Measuring Methods 3.1 Introduction Surface finish and texture can be measured in a large number of ways ranging from simply tracing a fingernail across a surface to the use of scanning electron microscopes (SEMs). Each particular method has its own advantages and disadvantages. If all techniques were to be covered in this book, there would be little room for anything else so we need to restrict ourselves. We will be concentrating on profilometry techniques because these are the most common. The range of surface topography measuring equipment can be divided into two classes, those used on- or in-line and those used in the laboratory. The former are quick and convenient, being typically two-dimensional (2D) profilometry and light scattering. The latter are mostly expensive and slow, being typically three- dimensional (313). Some of the latter techniques are exceedingly expensive and are only found in the larger laboratories, typically scanning electron microscopes (SEMs) and atomic force micro- scopes (AFMs). Areal techniques are growing in use but, apart from light scattering, are generally not used on-line. In view of this range, the emphasis in this chapter will be on stylus instruments, although towards the end, mention will be made of microscopy techniques. The most common method of assessing texture involves mechanically drawing a stylus across a surface. The principal elements for a 2D system are shown in Figure 3.1. The pickup supports the skid that rides over the surface. The stylus moves over

  Sign up to read

  Learn more about book
• 

  eBook - PDF

  Atomic Force Microscopy

  Imaging, Measuring and Manipulating Surfaces at the Atomic Scale

  • Victor Bellitto(Author)
  • 2012(Publication Date)
  • IntechOpen

    (Publisher)

  Non-contact mode is another useful Measurement of the Nanoscale Roughness by Atomic Force Microscopy: Basic Principles and Applications 151 mode for imaging soft surfaces, but its sensitivity to external vibrations and the inherent water layer on samples in ambient conditions often causes problems in the engagement and retraction of the tip. 3. Surface texture: Roughness, waviness and spacing Surface texture is an important issue when the main interest is to understand the nature of material surfaces and it plays an important role in the functional performance of many engineering components. The American National Standards Institute’s B46.1 specification defines surface texture as the repetitive or random deviation from the normal surface that forms the three dimensional topography of a surface. Before 1990’s the measurement of sample surface was obtained by a contact stylus profiler (Whitehouse et al., 1975) that had limitations including a large stylus radius, a large force and low magnification in the plane and may have misrepresented the real surface topography owing to the finite dimension of the stylus tip (Vorburguer & Raja, 1990). On the ultramicroscopic scale of surface, atomic force microscopy (AFM) has been developed to obtain a three-dimensional image of a material surface on a molecular scale. “Lay” is the term used to indicate the direction of the dominant pattern of texture on the surface. On a surface, the lay is in the front-to-back direction (Figure 6). Fig. 6. Surface lay (adapted from B. C. MacDonald & Co., 2011). Waviness (Figure 7) is the measure of the more widely spaced component of surface texture. It is a broader view of roughness because it is more strictly defined as the irregularities whose spacing, defined as the average spacing between waviness peaks, is greater than the roughness sampling length (Oberg et al., 2000).

  Sign up to read

  Learn more about book
• 

  eBook - ePub

  Tribology

  Friction and Wear of Engineering Materials

  • Ian Hutchings, Philip Shipway(Authors)
  • 2017(Publication Date)
  • Butterworth-Heinemann

    (Publisher)

  Equivalent functions for r.m.s. roughness, skewness, kurtosis, autocorrelation length etc. have all been defined for areal profiles. In addition, there are further parameters that can be derived only from areal profile information (such as the texture aspect ratio). Similarly, certain features of the areal surface profile can be characterized, which first involves identification of the features of interest. The features are generally classified as areal features (such as a hill), line features (such as a ridge) or point features (such as a peak). Once the features have been identified, then quantification can take place (such as the density of peaks, or the mean hill area).

  2.4 The Topography of Engineering Surfaces

  As a result of the manufacturing processes employed (for example, turning, milling or grinding), many surface finishes on engineering components exhibit directionality. This directionality is termed the lay , defined as the direction of the dominant surface pattern. If surfaces with a clear lay are characterized via a line profile, then standard methods of measurement generally require the line profile to run across the lay of the surface (i.e., perpendicular to the lay). The profile, and the measures of roughness derived from it, thus correspond to the maximum roughness of the surface, but give no information about the distribution of surface features in a direction along the lay, parallel to the machining marks. Figure 2.4 illustrates the distinct lay of a ground surface, and the contrasting lack of directionality of a shot-blasted surface.

  Height data gathered by profilometry may also be used to generate contour maps of surfaces, to study the statistics of feature distributions across two-dimensional areas, and to examine the area of contact between surfaces by numerically modelling their approach.

  The topography of a freshly-machined surface depends on the machining process used to generate it as well as on the nature of the material. Likewise, the topography of a worn surface depends on the conditions under which the wear has occurred.

  Sign up to read

  Learn more about book
• 

  eBook - PDF

  Surfaces and their Measurement

  • David J. Whitehouse(Author)
  • 2004(Publication Date)
  • Butterworth-Heinemann

    (Publisher)

  4 Surface metrology and manufacture 4.1 Where and when to measure Using the surface texture as a check on the process is well established but there are a number of issues to consider. These are: where to measure, what to measure and when to measure. Ideally, the measurement should take place as the workpiece is being made, so as to avoid scrapping more than one part. This in-process possibility is very diffi- cult to achieve because of the hostile environment in which the part is made. Often, it is the presence of metal chips and/or coolant spray that makes measurement dif- ficult but there is a trend towards dry cutting, which may help alleviate this problem. The number of parameters that could be measured and displayed in-process is limited although robust surface-measuring equipment cannot be expected to perform well. Another possibility is to have the surface tested when the part has been made but not moved. The surface instrument, which is hand-held, has somehow to be perched on the part when the machining has stopped and then the measurement recorded. Alternatively, the part could be removed from the machine (the lathe, say) and measured with an instrument located near to the machine tool. This is usually called in situ measurement and the availability of instrumentation with more parameters is much higher than in the in-process case. It would normally be the case that the in situ tests are carried out during every shift. The tests in the cases where the measurement is on or near the machine will be concerned with the process. Surface metrology and manufacture 97 For more rigorous tests involving perhaps roundness as well as roughness and waviness, the workpiece would be taken to a properly equipped inspection room. Here, some tests for machine tool capability would be possible. Failing this facility, the tests could be carried out at a 'centre of excellence' in which personnel as well as equipment are 'capable'.

  Sign up to read

  Learn more about book
• 

  eBook - ePub

  Fundamentals of Fluid Film Lubrication

  • Bernard J. Hamrock, Steven R. Schmid, Bo O. Jacobson(Authors)
  • 2004(Publication Date)
  • CRC Press

    (Publisher)

  µm. Even a highly polished surface, when examined microscopically or with a profilometer, has an irregular nature. The surface consists of high and low spots. The high spots, or protuberances, are called “asperities.”

  Surface Texture Measurement and evaluation can be quite complex; only a few surface parameters and measurement issues are discussed here. Standardized nomenclature is contained in industry standards ASME B46.1 (ASME, 1995a) and ASME Y14.36M (ASME, 1995b).

  A word of caution should be given that terms such as “rough”, “fine”, “smooth” and “super-smooth” should be avoided in describing the surface topography since the meaning is relative to the application being used. For example, a surface with Rq = 40 nm is considered “very rough” by people working in the field of optics, whereas a Rq =40 nm is considered “very smooth” for a machined surface.

  3.2     Geometric Characteristics of Surfaces

  The geometric characteristics, or texture, of surfaces as shown in Fig. 3.1 may conveniently be divided into three main categories:

  1. Error of form. The surface deviates from a well-defined pattern because of errors inherent in the manufacturing process.
  2. Waviness. Relatively long waves in a surface profile are often associated with unwanted vibrations that always occur in machine tool systems.
  3. Roughness. Irregularities, excluding waviness and error of form, are inherent in the cutting and polishing process during production.

  In the study of lubricated surfaces, roughness is the geometric variation that is generally of interest. Although often no sharp distinction can be drawn between these categories, roughness simply concerns the horizontal spacing (wavelength) of the surface features. From a practical point of view, in characterizing surfaces used in tribology both the vertical direction (or amplitude parameter) and the horizontal direction (or wavelength) are important.

  Sign up to read

  Learn more about book
• 

  eBook - ePub

  Mechanical Engineers' Handbook, Volume 1

  Materials and Engineering Mechanics

  • Myer Kutz(Author)
  • 2015(Publication Date)
  • Wiley

    (Publisher)

  So what is done is to take measurements from a small and representative sample of the surface so chosen that there is a high probability for the surface lying outside the sample to be statistically similar to that lying within the sample. Over the years different methods have been devised to study the topography of surfaces. A brief outline of some of the methods is presented here. 2.1 Surface Profilometer The most common method of studying surface texture features is the stylus profilometer, the essential features of which are illustrated in Fig. 2. A fine, very lightly loaded stylus is dragged smoothly at a constant speed across the surface under examination. The transducer produces an electrical signal, proportional to displacement of the stylus, which is amplified and fed to a chart recorder that provides a magnified view of the original profile. But this graphical representation differs from the actual surface profile because of difference in magnifications employed in vertical and horizontal directions. Surface slopes appear very steep on the profilometric record though they are rarely steeper than 10° in actual cases. The shape of the stylus also plays a vital role in incorporating error in measurement. The finite tip radius (typically 1–2.5 µm for a diamond stylus) and the included angle (of about 60° for pyramidal or conical shape) result in preventing the stylus from penetrating fully into deep and narrow valleys of the surface, and thus some smoothing of the profile is done. Some error is also introduced by the stylus in terms of distortion or damage of a very delicate surface because of the load applied on it. In such cases a noncontacting optical profilometer having optical heads replacing the stylus may be used. Reflection of infrared radiation from the surface is recorded by arrays of photodiodes, and analysis of the same in a microprocessor results in the determination of the surface topography

  Sign up to read

  Learn more about book
• 

  eBook - PDF

  Engineering Drawing for Manufacture

  • Brian Griffiths(Author)
  • 2002(Publication Date)
  • Butterworth-Heinemann

    (Publisher)

  6 Surface Finish Specification 6.0 Introduction Considering the trace of a supposedly flat surface in Figure 4.11, the 'flat' surface is far from a perfect straight line. Things related to the machine tool, such as vibrations and slide-way inaccuracies cause the long wavelength deviations where the undulations are of the order of millimetres. However, the figure also shows wavelengths of a much smaller magnitude. These deviations are the surface finish (SF). They are of the order of tens of microns and they are the machining marks. They are caused by a combination of the tool shape and the feed across the workpiece. In many instances the SF and texture can have a significant influence on functional performance (Griffiths, 2001). The SF is normally measured by a stylus, which is drawn across the surface to be measured. The stylus moves in a straight line over the surface driven by a traversing unit. This produces a 2D 'line' trace similar to that in Figure 4.11. A line trace produces an X-Y set of data points that can be analysed in a variety of statistical ways to produce parameters. These parameters are descriptors of a surface. They can be used to describe the SF of a surface in much the same way as a dimension describes the form of a feature. In the same way that a dimension can never be exact, the SF, represented by a parameter, can never be exact. Tolerances also need to added to SF specifications. To ensure fitness for purpose, the SF needs to be defined with limits. This chapter is concerned with the specification of SF and texture. 112 Engineering drawing for manufacture 6.1 Roughness and waviness A trace across a surface provides a profile of that surface which will contain short and long wavelengths (see Figure 4.11). In order for a surface to be correctly inspected, the short and long wavelength components need to be separated so they can be individually analysed.

  Sign up to read

  Learn more about book
• 

  eBook - ePub

  Innovative Technology in Art Conservation

  Original Appearance and Viewer Perception

  • W. (Bill) Wei(Author)
  • 2023(Publication Date)
  • Routledge

    (Publisher)

  When the author first entered the conservation field, he was talking to a paintings conservator about cleaning. The conservator was concerned that the painting he had just cleaned, that is, from which he had just removed the varnish, looked matt. The author thought, of course it does, you just removed the varnish. But in time, he learned that that was not the concern. The concern was that artists had known for centuries that varnishes worked best if they had the same or similar optical properties to the binder of the paint which the varnish covered, in particular, the property which is now known technically as the index of refraction. Thus, what the conservator was worried about was that the treatment he had used had not only removed the varnish but had also begun to remove the binder of the paint layer immediately below. Thus, the paint layer was more matt than he had expected.

  In the past, the initial response to such questions was based on chemical analysis. It is, however, now known that what the conservator was concerned about was not a result of the change in roughness due to the removal of the varnish itself, but the additional change in roughness due to the possible removal of binder from the paint. The remaining pigment particles would then stand out higher on the surface, increasing its roughness, and thus its matteness.

  The modern-day measurement of surface roughness, technically known as surface profilometry, has been in use since the first half to mid-20th century. Profilometry and the study of surface roughness is an important part of the engineering science of tribology, the study of friction, wear, and lubrication.

  Techniques for the measurement of surface roughness, that is, profilometry, have been commercially available since the mid-1950s. The first profilometers under the trade name Talysurf™ made use of a diamond needle/ stylus, much like that of an old phonograph needle, which was then drawn across the surface. One thus obtained a line profile, which reminds one of current-day profiles of a stage through the mountains of the famous Tour de France bicycle race. In fact, such a profile is actually a roughness line profile of the earth along the route of the stage. Besides a visualization of the surface roughness, quantitative data can be obtained by calculating various statistical parameters of the profile. Useful internationally standardized parameters for works of art include the average roughness, Ra , the mathematical average of all peaks and valleys about a mean line in absolute value (no negative or positive sign), and Rq, the so-called root-mean-square value which is more sensitive to height variations.

  There are two disadvantages to such contact profilometers, especially for studying works of art. First, a line profile says very little about the full or even just a part of a surface that a viewer is looking at. One can scan several lines next to each other to produce a three-dimensional surface profile, but with such stylus profilometers, it is extremely time-consuming, and the spatial resolution of a physical stylus depends on the radius of the stylus tip, which is often larger than the roughness effect one is trying to measure. Furthermore, the use of a diamond needle is, of course, a contact measurement which can damage the surface of the object, something not desirable in art conservation. Similar issues have had to be dealt with for the quality control of industrial parts and products.

  Sign up to read

  Learn more about book
• 

  eBook - PDF

  Engineering Tribology

  • John Williams(Author)
  • 2005(Publication Date)
  • Cambridge University Press

    (Publisher)

  These surface, as opposed to shape, variations are somewhat arbitrarily differentiated on the basis of wavelength into waviness (undulations with a relatively long wavelength, perhaps on the scale of millimetres) and roughness (variations which have a much shorter wave-length or correspondingly higher frequency); see Fig. 2.1. The distribution of both waviness and roughness may have a distinct directional component or lay, particularly if the final manufacturing process has been one such as turning or milling which possesses a strong directionality. Surfaces which have been finished by a non-directional method, such as electropolishing or lapping (provided this has removed all the traces of previous processes) may be much more homogeneous or isotropic in nature. Techniques of surface examination 39 (a) (c) Fig. 2.1 The components of surface topography: the total profile (a) represents the combined effects of waviness (b) and roughness (c) superimposed on the geometric shape or form of the component surface. 2.2 Techniques of surface examination The roughness of a surface affects many aspects of its behaviour and a variety of methods have been employed, each with considerable ingenuity, to assess and measure it. We shall see that it is not a straightforward matter to quantify roughness, especially if the aim is to use this quantitative assess-ment in predicting subsequent tribological behaviour. However, it would seem reasonable to suppose that roughness must be characterized by some information on heights normal to the mean plane of the surface together with some knowledge of the spatial distribution, or wavelengths, within the surface. We can thus classify the various methods available for topo-graphical examination according the range of vertical heights and spatial wavelengths they can each differentiate.

  Sign up to read

  Learn more about book
• 

  eBook - ePub

  Surface Modification of Textiles

  • Q Wei(Author)
  • 2009(Publication Date)
  • Woodhead Publishing

    (Publisher)

  2 Textile surface characterization methods Q. Wei; F. Huang; Y. Cai Jiangnan University, China Abstract This chapter introduces the most commonly used techniques for the surface analyses of textile materials including microscopic methods, spectroscopic techniques and surface wetting measurement. The microscopic techniques used in the analysis of textile surfaces mainly include scanning electron microscopy (SEM), transmission electron microscopy (TEM), environmental scanning electron microscopy (ESEM) and scanning probe microscopy (SPM). The basic working principles and the applications of spectroscopic techniques for textile surface characterization are also explained. Wetting and contact angle measurement are also discussed in this chapter. The measurement techniques described are the sessile drop method, the use of barrel-shaped droplets on a single fiber and measurement of dynamic contact angles using the Wilhelmy technique. Key words surface characterization scanning electron microscopy (SEM) environmental scanning electron microscopy (ESEM) scanning probe microscopy (SPM) Fourier transform infrared (FTIR) X-ray photoelectron spectroscopy (XPS) contact angle 2.1 Introduction Technological innovations and commercial demands for high-quality products have been driving the textile industry towards sophisticated and diverse markets with versatile products for a wide spectrum of applications ranging from agricultural, filtration, civil engineering, medical and hygiene, packaging, protective clothing, sportswear, transport, defense, leisure and safety (Ajmeri and Ajmeri, 2002). For these expanding applications of textiles, their surfaces are specially engineered to give the product its desired properties. In fact, unsuitable surface properties may negate the otherwise advantageous bulk properties of a particular polymer. For example, poor surface hydrophilic properties will render a fiber unsuitable for producing underwear

  Sign up to read

  Learn more about book
• 

  eBook - ePub

  Additive Manufacturing for the Aerospace Industry

  • Francis H. Froes, Rodney Boyer(Authors)
  • 2019(Publication Date)
  • Elsevier

    (Publisher)

  Ra of 94 and 13 µm, respectively, in perfect agreement with our surface roughness definition. In the next section, we will expand on the rationale employed to characterize the surface texture of AM-built components.

  16.2.3 Surface texture characterization of additive manufacturing components

  16.2.3.1 Introduction

  As we mentioned before, there are no specific standards to follow in order to do a proper surface texture characterization of AM-produced components, but there is a vast amount of literature addressing this issue that can be used as guidance [2] . Moreover, there are some basic steps that can be followed to get the best possible information from the obtained surface profile. The first point to address is the different techniques that can be used to interrogate the surfaces and discuss in brief their advantages and limitations. There are two main types of technologies available in the market to generate a surface profile: the contact and non-contact profilometers.

  16.2.3.2 Additive manufacturing surface characterization by contact profilometry

  We will begin our discussion by addressing the most basic and most widely used profilometer in the industry, the contact profilometer [2] . This technique works by the direct interaction (contact) of a probe tracing the surface, generating a two dimensional (2-D) data set of heights over a certain length of the surface. In this type of measurement, factors such as the probe size, shape, and skidded gages (waviness suppressed) are important and need to be specified when reporting measurements (best practice). Nevertheless, a considerable limitation of the contact probe method is that the probe will not be able to capture surfaces covered by inclined peaks (re-entrant), and the deepest features on the surface; this hampers the proper surface interrogation of AM components (Fig. 16.6 ). In addition, the characteristic granular surface of AM surfaces frequently causes jumps and temporary loss of contact, and, in some cases, lateral drifting of the probe, producing misleading data (Fig. 16.6 ) [29] . Nevertheless, contact profilometry is a very powerful tool and lots of information can be extracted from a proper trace [2]

  Sign up to read

  Learn more about book