Surface Characteristics and Quality Assurance

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CHAPTER 4

Surface Characteristics and Quality Assurance()


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Surface Structure of Metals

Figure 4.1 Schematic illustration of a cross-section of the surface structure of metals. The thicknessof the individual layers is dependent on processing conditions and processing environment.


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Terminology in Describing Surface Finish

Figure 4.2Standardterminology andsymbols to describe

surface finish. Thequantities are givenin in.


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Coordinates for Surface-Roughness

Measurements

Figure 4.3 Coordinates used for surface-roughness measurement, using Eqs. (4.1) and (4.2).


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Standard Lay Symbols for EngineeringSurfaces

Figureextra


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Measuring Surface Roughness

Figure 4.4 (a) Measuring surface roughness with a stylus. The rider supports the stylus and guardsagainst damage. (b) Surface measuring instrument. Source: Sheffield Measurement Division of Warner& Swasey Co. (c) Path of stylus in surface roughness measurements (broken line) compared to actualroughness profile. Note that the profile of the stylus path is smoother than that of the actual surface.

Source: D. H. Buckley

(b)


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Surface ProfilesFigure 4.4 Typical surface profiles produced by various machining and surface-finishing processes.Note the difference between the vertical and horizontal scales. Source: D. B Dallas (ed.), Tools andManufacturing Engineers Handbook, 3d ed. Copyright 1976, McGraw-Hill Publishing Company.Used with permission.


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Three-Dimensional Surface Measurement

Figure 4.4 extra Surface of rolled

aluminum.

Figure 4.4 extra A highly polishedsilicon surface measured in anatomic force microscope. The

surface roughness isRq = 0.134 nm.


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Contact Between Two Bodies

Figure 4.5 Schematicillustration of the interface of

two bodies in contact, showingreal areas of contact at theasperities. In engineeringsurfaces, the ratio of theapparent to real areas ofcontact can be as high as 4-5

orders of magnitude.


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Ring Compression Tests

(b)

Figure 4.7 Ring compression test between flat dies. (a) Effect of lubrication on type of ring specimen

barreling. (b) Test results: (1) original specimen and (2)-(4) increasing friction. Source: A. T. Male and M.G. Cockcroft.


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Effect of Wear on Surface Profiles

Figure 4.9 Changes inoriginally (a) wire-brushed and (b)ground-surface profilesafter wear. Source: E.

Wild and K. J. Mack.


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Types of Wear Observed in a Single Die

Figure 4.13 Types of wear observed in a single die used for hot forging. Source: T. A. Dean


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Types of Lubrication

Figure extra Types of lubrication generally occurring in metalworking operations. Source: AfterW.R.D. Wilson.


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Rough Surface

Figure 4.15 Rough surfacedeveloped on an aluminumcompression specimen by thepresence of a high-viscositylubricant and high compressionspeed. The coarser the grain size,the rougher the surface. Source: A.Mulc and S. Kalpakjian.


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Surface Treatments for Various MetalsTABLE 4.1

Metal Treatment

Aluminum Chrome plate; anodic coating, phosphate; chromateconversion coating

Beryllium Anodic coating; chromate conversion coating

Cadmium Phosphate; chromate conversion coating

Die steels Boronizing; ion nitriding; liquid nitriding

High-temperature steels Diffusion

Magnesium Anodic coating; chromate conversion coating

Mild steel Boronizing; phosphate; carburizing; liquid nitriding;

carbonitriding; cyaniding

Molybdenum Chrome plate

Nickel- and cobalt-base alloys Boronizing; diffusion

Refractory metals Boronizing

Stainless steel Vapor deposition; ion nitriding; diffusion; liquid nitriding;

nitriding

Steel Vapor deposition; chrome plate; phosphate; ion nitriding;

induction hardening; flame hardening; liquid nitriding

Titanium Chrome plate; anodic coating; ion nitriding

Tool steel Boronizing; ion nitriding; diffusion; nitriding; liquid nitriding

Zinc Vapor deposition; anodic coating; phosphate; chromate

chemical conversion coating

Source: After M. K. Gabel and D. M. Doorman in Wear Control Handbook, New York, ASME, 1980 p. 248.


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Roller Burnishing

Figure 4.16 Roller burnishing of the fillet of astepped shaft to induce compressive surfaceresidual stresses for improved fatigue life.

Figure 4.16 Examples of rollerburnishing of (a) a conical surfaceand (b) a flat surface and theburnishing tools used. Source:Sandvik, Inc.


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Thermal

SprayOperations

Figure extraSchematicillustrations ofthermal sprayoperations. (a)

Thermal wirespray. (b)Thermal metal-powder spray.(c) Plasmaspray.


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Sputtering

Figure extra Schematic illustration of the sputtering process. Source: ASM International


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Ion-Plating Apparatus

Figure extra Schematic illustration of an ion-plating apparatus. Source: ASM International.


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Chemical Vapor Deposition

Figure extra Schematic illustration of the chemical vapor deposition process.


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Electroplating

Figure extraSchematicillustration ofthe

electroplatingprocess.


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Electroplating Guidelines

Figure extra (a) Schematic illustration of nonuniform coatings (exaggerated) in electroplated parts.(b) Design guidelines for electroplating. Note that sharp external and internal corners should beavoided for uniform plating thickness. Source: ASM International.


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Hot Dipping

Figure extra Flowline forcontinuous hot-dip galvanizingof sheet steel. The welder(upper left) is used to weld theends of coils to maintain

continuous material flow.Source: American Iron andSteel Institute.


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Engineering Metrology andInstrumentation


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Analog and Digital Micrometers

(a)(c)

Figure extra (a) A micrometer being used to measure the diameter of round rods. Source: L. S.Starrett Co. (b) Vernier on the sleeve and thimble of a micrometer. Upper one reads 0.200 +0.075 + 0.010 = 0.285 in.; lower one reads 0.200 + 0.050 + 0.020 + 0.0003 = 0.2703 in. Thesedimensions are read in a manner similar to that described in the caption for Fig. 35.2. (c) Adigital micrometer with a range of 0-1 in. (0-25 mm) and a resolution of 0.00005 in. (0.001 mm).Note how much easier it is to read dimensions on this instrument than on the analog micrometershown in (a). However, such instruments should be handled carefully. Source: Mitutoyo Corp.


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Angle-Measuring Instruments

Figure extra (a) Schematicillustration of a bevelprotractor for measuringangles. (b) Vernier forangular measurement,indicating 14 30.

Figure extra Setup showing the use of asine bar for precision measurement ofworkpiece angles.


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Dial Indicators

Figure extra Setup showing the use of a sine bar for precision measurementof workpiece angles.


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Interferometry

Figure 4.18 (a)Interferometry method formeasuring flatness using anoptical flat. (b) Fringes on aflat inclined surface. An

optical flat resting on aperfectly flat workpiecesurface will not split the lightbeam, and no fringes will bepresent. (c) Fringes on asurface with two inclinations.

Note: the greater the incline,the closer the fringes. (d)Curved fringe patternsindicate curvatures on theworkpiece surface. (e) Fringepattern indicating a scratch on

the surface.


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Measuring Roundness

Figure extra (a) Schematic illustration of out of roundness (exaggerated). Measuringroundness using (b) V-block and dial indicator, (c) part supported on centers and rotated, and(d) circular tracing, with part being rotated on a vertical axis. Source: After F. T. Farago.


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Horizontal-Beam Contour Projector

Figure extra A bench model horizontal-beamcontour projector with a 16 in.-diameter screenwith 150-W tungsten halogen illumination.Courtesy ofL. S. Starrett Company, PrecisionOptical Division.


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Gages

Figure extra (a) Pluggage for holes, withGO-NOT GO onopposite ends. (b)Plug gage with GO-NOT GO on one end.(c) Plain ring gagesfor gauging roundrods. Note thedifference in knurledsurfaces to identifythe two gages. (d)Snap gage withadjustable anvils.

Figure 35.19 Schematicillustration of one type of

pneumatic gage.

Figure 4.20Basic size,d i ti d


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ToleranceControl

deviation, andtolerance on ashaft, according

to the ISOsystem.

Figure4.21 Various methods of assigning tolerances on a shaft.

Source: L. E. Doyle.


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Tolerances

as a Functionof Size

Figure 4.22 Tolerances as afunction of part size forvarious manufacturingprocesses. Note: Becausemany factors are involved,there is a broad range for

tolerances.


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E i i S b l


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Engineering Symbols

Figure extra Geometric characteristic symbols to be indicated on engineering drawings of parts to bemanufactured. Source: The American Society of Mechanical Engineers.


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Quality Assurance, Testing, andInspection


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Frequency Distribution Curve


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Frequency Distribution Curve

Figure 4.25

Frequencydistribution curve,showing lowerand upperspecification

limits.


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Constants for Control Charts


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TABLE 4.3

Sample size A2 D4 D3 d2

2

3

456

7

8910

1215

20

1.880

1.023

0.7290.5770.483

0.419

0.3730.3370.308

0.2660.223

0.180

3.267

2.575

2.2822.1152.004

1.924

1.8641.8161.777

1.7161.652

1.586

0

0

000

0.078

0.1360.1840.223

0.2840.348

0.414

1.128

1.693

2.0592.3262.534

2.704

2.8472.9703.078

3.2583.472

3.735

Figure 4.27 Controlcharts. (a) Processbegins to become outof control because ofsuch factors as tool


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Control Charts

such factors as toolwear (drift). The

tool is changed andthe process is then instatistical control.(b) Processparameters are notset properly; thus all

parts are around theupper control limit(shift in mean). (c)Process becomes outof control because offactors such as a

change in theproperties of theincoming material(shift in mean).


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Surface Characteristics and Quality Assurance

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