Ch33 surface roughness

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.ISBN 0-13-148965-8. © 2006 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.

Chapter 33Surface Roughness and Measurement;

Friction, Wear, and Lubrication


Surface Structure of Metals

Figure 33.1 Schematic illustration of a cross-section of the surface structure ofmetals. The thickness of the individual layers depends on both processingconditions and processing environment. Source: After E. Rabinowicz and B.Bhushan.


Terminology and SymbolsRelated to Surface Texture

Figure 33.2 (a) Standard terminology andsymbols used to describe surface finish.The quantities are given in µin. (b)Common surface lay symbols.


Surface-Roughness

Figure 33.3 Coordinates used forsurface-roughness measurement usingEqs. (33.1) and (33.2).

!

Ra =a +b+ c+d +K

n

Rq =a2

+b2

+ c2

+d2

+K

n


SurfaceRoughness

Figure 33.4 (a) Measuring surface roughness with a stylus. The rider supports thestylus and guards against damage. (b) Path of the stylus in surface-roughnessmeasurements (broken line) compared to the actual roughness profile. Note that theprofile of the stylus path is smoother than that of the actual surface. (c) through (f)Typical surface profiles produced by various machining and surface-finishing processes.Note the difference between the vertical and horizontal scales.


Real Contact Area

Figure 33.5 Schematic illustration of the interface of two bodies in contactshowing real areas of contact at the asperities. In engineering surfaces, theratio of the apparent-to-real areas of contact can be as high as 4 to 5 ordersof magnitude.


Ring-Compression Test

Figure 33.6 Ring-compression test between flat dies. (a) Effect of lubrication ontype of ring-specimen barreling. (b) Test results: 1. original specimen and 2. to 4.increasing friction. Source: After A. T. Male and M. G. Cockcroft.


FrictionCoefficient Chart

Figure 33.7 Chart to determine friction coefficient from a ring-compression test.Reduction in height and change in internal diameter of the ring are measured; then µ isread directly from this chart. For example, if the ring specimen is reduced in height by40% and its internal diameter decreases by 10%, the coefficient of friction is 0.10.


WornSurfaces

Figure 33.8 Changes in original (a) wire-brushed and (b) ground-surfaceprofiles after wear. Source: After E. Wild and K. J. Mack


Adhesive and Abrasive Wear

Figure 33.9 Schematic illustration of (a) two contracting asperities, (b)adhesion between two asperities, and (c) the formation of a wear particle.

Figure 33.10 Schematic illustration of abrasive wear in sliding.Longitudinal scratches on a surface usually indicate abrasive wear.


Types of Wear in Hot Forging Die

Figure 33.11 Types of wear observed in a single die usedfor hot forging. Source: After T. A. Dean.


Lubrication Types

Figure 33.12 Types of lubrication generally occurring inmetalworking operations. Source: After W. R. D. Wilson.

Ch33 surface roughness

Engineering

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