Most models of surface contact consider the surface roughness to be on one of the contacting surfaces only. The authors give a general theory of contact between two rough plane surfaces. They show that the important results of the previous models are unaffected: in particular, the load and the area of contact remain almost proportional, independently of the detailed mechanical and geometrical properties of the asperities. Further, a single-rough-surface model can always be found which will predict the same laws as a given two-rough-surface model, although the required model may be unrealistic. It does not seem possible to deduce the asperity shape or deformation mode from the load-compliance curve.

http://journals.sagepub.com/doi/pdf/10.1243/PIME_PROC_1970_185_069_02

The Contact of Two Nominally Flat Rough Surfaces

The past few decades have seen substantial growth in Additive Manufacturing (AM) technologies. However, this growth has mainly been process-driven. The evolution of engineering design to take advantage of the possibilities afforded by AM and to manage the constraints associated with the technology has lagged behind. This paper presents the major opportunities, constraints, and economic considerations for Design for Additive Manufacturing. It explores issues related to design and redesign for direct and indirect AM production. It also highlights key industrial applications, outlines future challenges, and identifies promising directions for research and the exploitation of AM's full potential in industry.

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Design for additive manufacturing: trends, opportunities, considerations, and constraints

A review of techniques, advances and outstanding issues in numerical modelling for rock mechanics and rock engineering

This paper describes a study of the adhesion between elastic solids and the effect of roughness in reducing the adhesion. The experiments were carried out between optically smooth rubber spheres and a hard smooth flat surface of Perspex which could be roughened to various degrees. The radius of the rubber spheres was varied by a factor of 8, their elastic modulus by a factor of 10, while the centre line average (c.l.a.)of the roughened Perspex surface was varied from 0.12 to 1.5 μm. The results show that c.l.a. roughnesses which are small compared with the overall deformation occurring at the region of the rubber-Perspex contact can produce an extremely large reduction in adhesion. The effect is more marked for rubbers of higher modulus. On the other hand the curvature of the sphere (over the range examined) has little influence. For this reason and because the analytical problem of a sphere on a rough flat is extremely complicated a theoretical analysis has been developed for the simpler case of a smooth flat in contact with a rough flat surface. As in Greenwood & Williamson (1966) the rough surface is modelled by asperities all of the same radius of curvature and with heights following a Gaussian distribution of standard deviation σ. The overall contact force is obtained by applying the contact theory of Johnson, Kendall & Roberts (1971) to each individual asperity. The theory predicts that the adhesion expressed as a fraction of the maximum value depends upon a single parameter, 1/Δ e ,which is the ratio between a and the elastic displacement δ C that the tip of an asperity can sustain before it pulls off from the other surface. The analysis shows that the adhesion parameter may also be regarded as representing the statistical average of a competition between the compressive forces exerted by the higher asperities trying to prize the surfaces apart and the adhesive forces between the lower asperities trying to hold the surfaces together. Although the theory is derived for two nominally plane surfaces it is found to fit the experimental results for a sphere on a flat reasonably well.

/pdf/the-effect-of-surface-roughness-on-the-adhesion-of-elastic-4kb8spmx92.pdf

The effect of surface roughness on the adhesion of elastic solids

For measuring machines and machine tools, geometrical accuracy is a key performance criterion. While numerical compensation is well established for CMMs, it is increasingly used on machine tools in addition to mechanical accuracy. This paper is an update on the CIRP keynote paper by Sartori and Zhang from 1995 [Sartori S, Zhang GX (1995) Geometric error measurement and compensation of machines, Annals of the CIRP 44(2):599–609]. Since then, numerical error compensation has gained immense importance for precision machining. This paper reviews the fundamentals of numerical error compensation and the available methods for measuring the geometrical errors of a machine. It discusses the uncertainties involved in different mapping methods and their application characteristics. Furthermore, the challenges for the use of numerical compensation for manufacturing machines are specified. Based on technology and market development, this work aims at giving a perspective for the role of numerical compensation in the future.

Geometric error measurement and compensation of machines : an update

In recent work it has been shown that many types of surfaces used in engineering practice have a random structure. The paper takes, as a representation of the profile of such a surface, the waveform of a random signal; this is completely defined by two parameters, a height distribution and an auto-correlation function. It is shown how such a representation can be transformed into a model, appropriate for the study of surface contact, consisting of an array of asperities having a statistical distribution of both heights and curvatures. This theory is compared with the results of an analysis of surface profiles presented in digital form. The significance of these findings for the theory of surface contact and for the measurement and characterization of surface finish is discussed.

The properties of random surfaces of significance in their contact.

/pdf/the-properties-of-random-surfaces-of-significance-in-their-2dh812uy4a.pdf

The Properties of Random Surfaces of Significance in their Contact

Foreword by Professor D. Dowson GENERAL PHILOSOPHY OF MEASUREMENT Where does surface metrology fit in engineering metrology? Importance of surface metrology SURFACE CHARACTERIZATION-THE NATURE OF SURFACES AND THE SIGNALS OBTAINED FROM THEM Surface roughness characterization Waviness Errors of form Comparisons of definitions for surface metrology and coordinate measuring Characterization of defect shapes on the surface PROCESSING Digital methods Digital properties of random surfaces Fourier transform and the FFT Statistical parameters in digital form Properties and implementation of ambiguity function and Wigner distribution function Digital estimation of reference lines for surface metrology Algorithms Transformation in surface metrology Graphical methods Other methods of processing Surface generation INSTRUMENTATION Introduction and historical Measurement systems Optical techniques for measurement of surfaces Capacitance techniques for measurement of surfaces of slopes Inductance techniques Impedance technique-skin effect Other non-standard techniques Electron microscopy Merit of transducers ERRORS, CALIBRATION, TRACEABILITY AND STANDARDIZATION Nature of errors Deterministic or systematic error model Basic components of accuracy evaluation Basic error theory for a system Propagation of errors Some useful statistical tests for surfaces Uncertainty in instruments-calibration in general Calibration of stylus instruments Calibration of form instruments Parameter variation National and international standards Drawing symbols SURFACE METROLOGY IN MANUFACTURE Manufacturing processes Cutting Abrasive processes Unconventional machining Surface roughness produced by machining difficult materials Surface effects other than geometry Surface geometry-a fingerprint of manufacture SURFACE GEOMETRY-ITS IMPORTANCE IN FUNCTION Two body interaction - static effects Functional properties of contact Two body interactions - dynamic effects General roughness and system life One body interactions One body with radiation (optical) Scattering by other waves Systems function SUMMARY AND CONCLUSIONS Characterization and nature of signal Data processing Measurement of trends Calibration Manufacture Function Overview

Handbook of Surface Metrology

Introduction-Surface and Nanometrology General Surface Metrology Background to Surface Metrology Nanometrology Book Structure Characterization The Nature of Surfaces Surface Geometry Assessment and Parameters Characterization Waviness Errors of Form Characterization of Structured and Free Form Surfaces Characterization of Defects on the Surface Discussion Processing, Operations, and Simulations Digital Methods Discrete (Digital) Properties of Random Surfaces Digital Form of Statistical Analysis Parameters Digital Estimation of References for Surface Metrology Algorithms and Mathematical Techniques Basic Concepts in Linear Programming Fourier Transforms and the Fast Fourier Transform Transformations in Surface Metrology Space-Frequency Functions Surface Generation Atomistic Considerations and Simulations Summary Measurement Techniques Background Measurement Systems Stylus-Micro Measuring Instruments Stylus-Nano/Atomic Scale Optical Techniques Capacitance and Other Techniques Electron Microscopy, Photon Microscopy, Raman Spectrometry Comparison of Techniques-General Summary Some Design Considerations Standardization-Traceability-Uncertainty Introduction Nature of Errors Basic Error Theory Propagation of Errors Statistical Tests for Surface Metrology Uncertainty in Instruments-Calibration in General The Calibration of Stylus and Other Instruments Calibration of Form Instruments Variability of Surface Parameters Gps System-International and National Standards Specification for CAD and on Drawings Summary Surfaces and Manufacture Introduction Manufacturing Processes Cutting Abrasive Processes Unconventional Processes Forming Processes Effect of Scale of Size in Manufacture: Macro to Nano to Atomic Processes Structured Surface Manufacture Manufacture of Free-Form Surfaces Mathematical Processing of Manufacture-Finite Element Analysis (Fe), Md, Nurbs The Subsurface and the Interface Surface Integrity Surface Geometry-A Fingerprint of Manufacture Surface Finish Effects in Manufacture of Microchip Electronic Components Discussion and Conclusions Surface Geometry and Its Importance in Function Introduction Two-Body Interaction-The Static Situation Macro to Nanoscale, Contact, Adhesion Corrosion Two-Body Interactions-Dynamic Behavior Macro to Nanoscale, Friction, Wear, Lubrication One-Body Interactions- Optical Scatter, Diffraction System Function Multi-Surfaces Assembly Discussion Conclusions Surface Geometry, Scale of Size Effects, Nanometrology Introduction Effect of Scale of Size on Surface Geometry Scale of Size, Surface Geometry, and Function Scale of Size and Surfaces in Manufacture Nano Instrumentation Operation and Design Considerations Standards, Traceability, and Uncertainty at the Nanoscale Measurement of Typical Nanofeatures Measuring Length to Nanoscale with Interferometers and Other Devices Nano Geometry in Macro Situations Discussion and Conclusions General Comments Introduction Characterization Processing, Operations, and Simulations Measurement Techniques Traceability Standardization Uncertainty Surfaces and Manufacture Surface Geometry and Performance Nanometrology Overview Glossary Index References appear at the end of each chapter.

David J. Whitehouse

Papers

The properties of random surfaces of significance in their contact.

The Properties of Random Surfaces of Significance in their Contact

Handbook of Surface Metrology

Handbook of Surface Metrology

Handbook of Surface and Nanometrology