Radiography in Modern Industry - Kodak

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Figure 114: Characteristic curve of a typical industrial x-ray film. Gradients have beenevaluated at two points on the curve.Now consider two slightly different thicknesses in a specimen. These transmit slightly differentintensities of radiation to the film; in other words, there is a small difference in the logarithm of therelative exposure to the film in the two areas. Let us assume that at a certain kilovoltage thethinner section transmits 20 percent more radiation than the thicker. The difference in logarithm ofrelative exposure (∆ log E) is 0.08, and is independent of the milliamperage, exposure time, orsource-film distance. lf this specimen is now radiographed with an exposure that puts thedeveloped densities on the toe of the characteristic curve where the gradient is 0.8, the x-rayintensity difference of 20 percent is represented by a density difference of 0.06 (See Figure 115).If the exposure is such that the densities fall on that part of the curve where the gradient is 5.0,the 20 percent intensity difference results in a density difference of 0.40.Radiography in Modern Industry 184
Figure 115: Characteristic curve of a typical industrial x-ray film. Density differencescorresponding to a 20 percent difference in x-ray exposure have been evaluated for thetwo values of gradient illustrated in Figure 114.In general, if the gradient of the characteristic curve is greater than 1.0, the intensity ratios, orsubject contrasts, of the radiation emerging from the specimen are exaggerated in theradiographic reproduction, and the higher the gradient, the greater is the degree of exaggeration.Thus, at densities for which the gradient is greater than 1.0, the film acts as a "constant amplifier".Similarly, if the gradient is less than 1.0, subject contrasts are diminished in the radiographicreproduction.A minimum density is often specified for radiographs. This is not because of any virtue in aparticular density, but rather because of the gradient associated with that density. The minimumuseful density is that density at which the minimum useful gradient is obtained. In general,gradients lower than 2.0 should be avoided whenever possible.The ability of the film to amplify subject contrast is especially significant in radiography with verypenetrating radiations, which produce low subject contrast. Good radiographs depend on theenhancement of subject contrast by the film.The direct x-ray characteristic curves of three typical x-ray films are shown in the first figurebelow. The gradients of these curves have been calculated, and are plotted in the second figurebelow against the density. It can be seen that the gradients of Films X and Y increasecontinuously up to the highest densities that can conveniently be used in radiography. This is thebasis for the recommendation that with these films one should use the highest densities that theavailable illuminators allow to be viewed with ease. The gradient versus density curve of Film Zhas a form different from the others in that the gradient increases, then becomes essentiallyconstant over the density range of about 1.5 to 2.5, beyond which it decreases. With this film, thegreatest density difference corresponding to a small difference in transmission of the specimen isobtained in the middle range of densities and the maximum, as well as the minimum, usefuldensity is governed by the minimum gradient that can be tolerated.Radiography in Modern Industry 185
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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
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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 and 182: such that it does not distort the i
Page 183: Figure 113: A: Representation of a
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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