Radiography in Modern Industry - Kodak

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Chapter 16: Sensitometric Characteristics of X-rayFilmsThe Characteristic CurveThe relation between the exposure and the density in the processed radiograph is commonlyexpressed in the form of a characteristic curve, which correlates density with the logarithm ofrelative exposure.Photographic density is dimensionless, since it is the logarithm of a dimensionless ratio. Thereare, therefore, no "units" of density. In this respect, it is similar to a number of other physicalquantities, for example, pH, specific gravity, and atomic weight.ContrastThe slope, or steepness, of the characteristic curve for x-ray film changes continuously along itslength. (See "The Characteristic Curve".) The density difference corresponding to a difference inspecimen thickness depends on the region of the characteristic curve on which the exposuresfall. The steeper the slope of the curve in this region, the greater is the density difference, andhence the greater is the visibility of detail. (This assumes, of course, that the illuminator is brightenough so that a reasonable amount of light is transmitted through the radiograph to the eye ofthe observer.)The increasing ease of visibility of detail with increasing steepness of the characteristic curve isdemonstrated in Figure 113. Figure 113B and C of the figure below are radiographs of the testobject shown in Figure 113A. The radiographs differ only in the milliampere-seconds used tomake them, that is, on the portion of the characteristic curve on which the densities fall. Thedetails are much more clearly visible on radiograph C than on B because C falls on the steeperhigh-density portion of the characteristic curve (where the film contrast is high), while B falls onthe much flatter toe portion.
Figure 113: A: Representation of a photograph of the test object. B and C: Radiographs ofthe test object. The exposure time for C was greater than that for B, all other factorsremaining constant. Note that the structure of the test object is more clearly seen in C,since it was made on a steeper portion of the characteristic curve.The type of example dealt with qualitatively, above, also lends itself to quantitative treatment.The slope of a curve at any particular point may be expressed as the slope of a straight linedrawn tangent to the curve at the point. When applied to the characteristic curve of aphotographic material, the slope of such a straight line is called the gradient of the material at theparticular density. A typical characteristic curve for a radiographic film is shown in the figurebelow. Tangents have been drawn at two points, and the corresponding gradients (ratios a/b,a'/b') have been evaluated. Note that the gradient varies from less than 1.0 in the toe to muchgreater than 1.0 in the high-density region.Radiography in Modern Industry 183
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RadiographyinModernIndustry
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RadiographyinModernIndustryFOURTH E
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ContentsIntroduction...............
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Chapter 1: The Radiographic Process
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Intensifying ScreensX-ray and other
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makes it a very suitable material f
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Figure 6: Typical voltage waveforms
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Table I - Typical X-ray Machines an
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The wavelengths (or energies of rad
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Table III - Industrial Gamma-Ray So
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1. The source of light should be sm
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B and H in the Figure 13 show the e
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Figure 14: Geometric construction f
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Figure 17: Pinhole pictures of the
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The kilovoltage applied to the x-ra
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Figure 21: Schematic diagram of som
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kind of material radiographed, the
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instance, the kilovoltage may be fi
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The technique need not be limited t
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Chapter 5: Radiographic ScreensWhen
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Contact between the film and the le
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Figure 29: The number of electrons
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lead foil screens ran be retained w
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Figure 33: The sharpness of the rad
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Figure 34: Low density (right) is a
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such as a wall or floor, on the fil
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from this source. Since scatter als
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A filter reduces excessive subject
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Definite rules as to filter thickne
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0.010-inch front screen of value be
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Example: Suppose that with a given
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If the milliamperage remains consta
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espectively. In other words, a cons
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Any given exposure chart applies to
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Figure 46: Typical gamma-ray exposu
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where the slope of the characterist
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Figure 49: Characteristic curves of
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Figure 51: Characteristic curve of
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Nomogram MethodsIn Figure 54, the s
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Figure 56: Transparent overlay posi
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Figure 58: Overlay positioned so as
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The problem of radiographing a part
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Figure 62: System of lines drawn on
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Chapter 8: Radiographic Image Quali
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Film contrast refers to the slope (
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Hole Type PenetrametersThe common p
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of the same thickness as the specim
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Chapter 9: Industrial X-ray FilmsMo
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Figure 70 indicates the direction t
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the lead letters on a radiation-abs
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Therefore, protection requirements
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5. Avoid pressure damage caused by
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Paddles or plunger-type agitators a
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slow, and the development time reco
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ubbles make their way to the surfac
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When development is complete, the f
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soften considerably with prolonged
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Figure 77: The roller transport sys
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Rapid Access to Processed Radiograp
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Figure 78: Film-feeding procedures
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Chapter 11: Process ControlUsers of
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3. Age of the developer replenisher
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Figure 80: Control chart below for
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DiscussionDensitometric data and pr
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Figure 82: Plan of a manual x-ray p
Page 131 and 132: Figure 83: A schematic diagram of a
Page 133 and 134: loading-bench activities are carrie
Page 135 and 136: KODAK Quinone-Thiosulfate Intensifi
Page 137 and 138: Methylene-Blue MethodTwo variations
Page 139 and 140: KODAK Hypo Test Solution HT-2Avoird
Page 141 and 142: In summary, use of the test papers
Page 143 and 144: narrow angle would be very thick, e
Page 145 and 146: When radiation passes through a spe
Page 147 and 148: Figure 89: Demonstration of the eff
Page 149 and 150: Figure 90: The amount of gamma radi
Page 151 and 152: The radiograph exposed in the right
Page 153 and 154: To illustrate, let us assume that t
Page 155 and 156: Figure 95: High-speed x-ray picture
Page 157 and 158: Figure 97: Two methods of neutron r
Page 159 and 160: Duplicating RadiographsSimultaneous
Page 161 and 162: Sometimes, as when sets of referenc
Page 163 and 164: PhotofluorographyIn photofluorograp
Page 165 and 166: discontinuities or of segregation i
Page 167 and 168: from the camera or by reaching down
Page 169 and 170: Figure 106: Schematic diagram of th
Page 171 and 172: valuable technique, for instance, i
Page 173 and 174: The position of the spots is determ
Page 175 and 176: Powder Diffraction File, Internatio
Page 177 and 178: Processing TechniquesRadiographs on
Page 179 and 180: Since this formula applies only to
Page 181: such that it does not distort the i
Page 185 and 186: Figure 115: Characteristic curve of
Page 187 and 188: film fairly well. If high densities
Page 189 and 190: Density = 1.5 Density = 2.5Film Rel
Page 191 and 192: In most industrial radiography, the
Page 193 and 194: e noted here. Although the average
Page 195 and 196: Chapter 17: Film Graininess; Signal
Page 197 and 198: The ratio of signal to noise has a
Page 199 and 200: Chapter 18: The Photographic Latent
Page 201 and 202: Thus, the change that makes an expo
Page 203 and 204: Figure 130: Stages in the developme
Page 205 and 206: electrons by successive Compton int
Page 207 and 208: Development is essentially a chemic
Page 209 and 210: Chapter 19: ProtectionOne of the mo
Page 211 and 212: duct is brought into the x-ray room
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Radiography in Modern Industry - Kodak

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