Surface Texture
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Surface Texture Richard Leach* Department of Mechanical, Materials and Manufacturing Engineering, University of Nottingham, Nottingham, UK
Definition Surface texture is the geometrical irregularities present at a surface. Surface texture does not include those geometrical irregularities contributing to the form or shape of the surface.
Theory and Application Most manufactured parts rely on some form of control of their surface characteristics. The surface is usually defined as the feature on a component or device that interacts with the environment, in which the component is housed or in which the device operates, or with another surface (Leach et al. 2014). The surface topography, and of course the material characteristics, of a part can affect how two bearing parts slide together, how fluids interact with the part, or how the part looks and feels (Bruzzone et al. 2008; Thomas 2014). Surface topography is defined (in Leach 2014) as the overall surface structure of a part (i.e., all the surface features treated as a continuum of spatial wavelengths), surface form as the underlying shape of a part (e.g., a cylinder liner has cylindrical form), and surface texture as the features that remain once the form has been removed (e.g., machining marks on the cylinder liner). The origins of the surface texture on an object come from a number of sources. Any surface that has been manufactured will have some production process marks, which are inherent and which are caused by the tool removing material or any additive processes. Surface texture also comprises other marks on the surface which are not inherent and which are produced by errors of one sort or another, such as the machine tool lack of stiffness resulting in chatter of the tool against the workpiece, thermal effects such as deflections, or agglomeration of particulates in an additive process, and material effects producing surface irregularities, such as grain boundaries.
Surface Texture Measurement Surface geometry can be measured using a variety of physical principles, but the most common methods use contacting or optical techniques. The measurement principles fall in to two categories as follows: 1. Those that measure surface topography directly. Such methods produce a topographical image of the surface that may be represented mathematically as a height function, z(x) in the profile case and z(x,y) in the areal case (see below). From the topography image, various filtering processes are used to extract the surface texture. 2. Those that measure a representative area of a surface and produce numerical results that depend on area-integrated properties of the surface. Such methods interrogate physical models of the
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CIRP Encyclopedia of Production Engineering DOI 10.1007/978-3-642-35950-7_16799-1 # CIRP 2014
Fig. 1 Top: primary profile, center: waviness, bottom: roughness (Courtesy Leach 2014)
interaction of the instrument with the surface to directly produce parameters of the surface texture. The reader is referred
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