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Proposed corrections for the ISO 25178 standard series on areal surface texture

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... They are useful for tribological applications. It is also possible to calculate the number of open or closed motifs at a particular depth, which is useful for applications related to lubrication [12,13]. ...
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Segmentation of profile features is mainly described in two standards: ISO 4287 for profile elements, used to calculate RSm and Rc, and ISO 12085 for profile motifs, used to calculate R&W parameters. These methods are commonly criticised for their unstability, although they provide valuable results when used in an adequate context. A new profile segmentation based on watersheds is introduced in ISO 21920-2 and ISO 16610-45, on the model of areal feature parameters [Blateyron 2013], with the hope to solve most of the existing problems. However, there are very few comparisons between these methods and almost no recommendations for the configuration of the segmentation. This paper discusses the validity of applying segmentation methods on certain profiles and proposes a validity criterion. It also introduces a new method to determine an Optimal Limit A for the Motifs method. Finally, it investigates algorithmic differences between the watershed segmentation and the classical Motifs method, compares the results between the two methods, and suggests a guideline of good practices.
... The difference is due to an approximation of the computation method implemented in SurfStand [2]. ...
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Current definitions and computation of areal surface texture parameters are based on planar, measured or unwrapped, surface which is not applicable for non planar irregular meshes. In this paper an extension of areal surface texture parameters (height and hybrid parameters) for freeform surface is proposed. The proposed method can be used for both general and complex surfaces and it works well on surfaces where there are undercuts and non uniformly spaced points. The proposed method has been tested on six sets of different types of surfaces and the computed parameter results were compared with the values of the parameters defined in ISO 25178-2:2012.
Chapter
Unlike field parameters, where every point on the surface is considered in the calculation, the category of feature parameters only uses identified features on the surface. Features are considered because they play a significant role in a particular function, for example, large peaks and hills play a functional role as contact zones in mechanical engineering applications, while points located in valleys do not. Significant features are identified by segmentation of the surface and are selected by a discrimination method known as pruning. Parameters are then calculated to quantify the characteristics of the selected features.
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In the papermaking process it is a well-known fact that the flow condition of a free jet entering the former section has a direct influence on the structure of the final paper. In this paper we present a systematic analysis how surface roughness and MD characteristic size of the slice jet depend on jet velocity, jet length, pulp consistency and vane geometry. The measurements are based on laser profiling and ccd-imaging.
Chapter
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The vast majority of surface texture parameters are the field parameters. The term field refers to the use of every data point measured in the evaluation area, as opposed to feature parameters that only take into account specific points, lines or areas. Field parameters allow the characterisation of surface heights, slopes, complexity, wavelength content, etc. They are defined in the specification standard ISO 25178 part 2. In this chapter the ISO areal field parameters will be presented along with limited guidance on their use.
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Reference software for the evaluation of a set of areal surface texture parameters is described, focusing on the definitions of the parameters and giving details of the numerical algorithms employed in the software to implement those definitions. The main consideration in the design and development of reference software is its numerical correctness, and the algorithms chosen and the implementations of those algorithms reflect this consideration. The surface for which parameters are to be evaluated is a bicubic spline interpolant to the available discretely-sampled data, and parameters are evaluated for that continuous surface either to a high numerical precision or to a numerical precision that is under the control of the user.
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This is the second part of the paper ‘Paradigm shifts in surface metrology’. In part I, the three historical paradigm shift in surface metrology were brought together, and the subsequent evolution resulting from the shifts discussed. The historica philosophy highlighted the fact that the paradigm shifts must be robust and flexible, meaning that surface metrology mus allow for full control of surface manufacture and provide an understanding of the surface functional performance. Part I presents the current paradigm shift as a ‘stepping stone’, building on the above historical context. Aspects of surface geometr will also have to cater for surfaces derived from disruptive application, i.e. structured and freeform surfaces are identifie candidates. The current shift is presented in three aspects: from profile to areal characterization; from stochastic to structure surfaces; and from simple geometries to complex freeform geometries, all spanning the millimetre to sub-nanometre scales. In this paradigm shift, the scale of surface texture is beginning to approach some of the geometrical features in micro/nan electro-mechanical systems devices and is becoming one of the most important functionality indicators. Part II will contextualiz the current shifts in the discipline of surface metrology, and cement surface metrology in place in the ultra precision an nanotechnology age.
Article
The paper follows the formal approach by J. L. Pfaltz (Pfaltz, 1976). A contraction that permits the simplification of a surface network by elimination of marginal peaks and pits is described. Additionally it is shown that all surface networks can be reduced by combining Pfaltz's and the above-mentioned contraction until an 'elementary surface network' is obtained.
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This paper examines the use of some differential formulae in the context of surface texture profile analysis. After a theoretical analysis, their behavior on real profiles was studied. It is shown that simple models of real profiles are adequate to predict the observed behavior and so allow a judgment to be made on the accuracies of the formulae under real conditions.
Article
3D parameters are important in tribological studies and many of them show strong correlation with surface operational performance. Characterization of cylinder liner surfaces is a good example of the use of 3D roughness parameters. Standard ISO 25178-2:2012 defines new parameters retaining some of the old ones, even though presented as their equivalent 3D successors. That is the case for instance of the “k” series: Spk, Svk and Sk. This paper covers an analysis of the relationship between Spk and the new volume parameter Vmp where it is shown that it is not correct to designate Spk as the average height of the protruding peaks above the core surface as stated in the standard. It is also suggested that Sk should be maintained but that the new volume parameters, through their relationship to the “k series”, make it possible to discard Spk and Svk.
Book
The function of a component part can be profoundly affected by its surface topography. There are many examples in nature of surfaces that have a well-controlled topography to affect their function. Examples include the hydrophobic effect of the lotus leaf, the reduction of fluid drag due to the riblet structure of shark skin, the directional adhesion of the gecko foot and the angular sensitivity of the multi-faceted fly eye. Surface structuring is also being used extensively in modern manufacturing. In this way many properties can be altered, for example optical, tribological, biological and fluidic. Previously, single line (profile) measurements were adequate to control manufacture of surfaces, but as the need to control the functionality of surfaces increases, there is a growing need for three-dimensional (areal) measurement and characterisation techniques. For this reason there has been considerable research, development and standardisation of areal techniques. This book will present the areal framework that is being adopted by the international community. Whereas previous books have concentrated on the measurement aspects, this book concentrates on the characterisation techniques, i.e. how to interpret the measurement data to give the appropriate (functional) information for a given task. The first part of the book presents the characterisation methods and the second part case studies that highlight the use of areal methods in a broad range of subject areas - from automobile manufacture to archaeology. © 2013 Springer-Verlag Berlin Heidelberg. All rights are reserved.
Chapter
Unlike field parameters, where every point on the surface is taken into account in the calculation, the category of feature parameters takes into account only identified features on the surface. Features are considered because they play a significant role in a particular function (for example, large peaks and hills play a functional role as contact zones in mechanical engineering applications; while points located in valleys do not). Significant features are identified by segmentation of the surface and selected by a discrimination method known as pruning. Parameters are then calculated to quantify the characteristics of the selected features.
Article
More than a hundred years ago Maxwell proposed dividing a landscape into regions consisting of hills or alternatively consisting of dales. A hill is a set of points from which maximum uphill paths lead to one particular peak, and a dale is the set of points from which maximum downhill paths lead to one particular pit.Starting with Maxwell's ideas this paper sets out to develop the foundations of topological characterization of surface texture. This leads to a system of surface texture characterization which is complementary to published areal parameters based on the mean line system. In a similar manner that R&W system is complementary to the mean line system for profiles (the dale is the areal equivalent of a motif on a profile).An important example of a true areal characterization contained within this system is the connectability of surface valleys. This is important for applications such as lubrication and paintability of a surface. It is also important for characterizing extruded aluminium that has been anodized. The anodizing has cracks (connected valleys) and isolated pits, both of which require characterizing separately for production control.