Radiography in Modern Industry - Kodak

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MicroradiographySometimes--usually with thin specimens of low x-ray absorption--the detail required for study istoo fine to be seen with the naked eye, and examination of the image through a low poweredmicroscope or enlargement of the radiograph by ordinary optical projection, is required tovisualize the available detail. This method, microradiography, generally employs soft x-raysgenerated in the range of 5 to 50 kV. The photographic emulsion is usually single coated andfiner grained than the emulsion of ordinary x-ray films.Commercial applications of microradiography have included such unrelated projects as studyingcemented joints in corrugated cardboard, and distinguishing between natural and cultured pearls.Biological materials, such as tissue sections, insects, and seeds, have been examined. Inhorticulture, the distribution of inorganic spray materials on foliage has been investigated bymeans of microradiography. Of particular interest to the metallurgist is the demonstration ofminute discontinuities and the segregation of the constituents of an alloy in a thin section (SeeFigure 102).Figure 102: Microradiograph of leaded brass made on a very slow photographic plate oflow graininess. Enlargement is about 150 diameters.Figure 103: Microradiograph of a cast aluminum alloy containing about 8 percent copper,made on a slow photographic plate of low graininess. Light areas are copper-rich.Enlargement is 35 diameters.Both the continuous, or "white", x-radiation and the characteristic K spectrum from a suitabletarget find use in microradiography. The continuous spectrum can be used for detection of minuteRadiography in Modern Industry 164
discontinuities or of segregation in alloys in which the components differ fairly widely in atomicnumber--for example, the examination of aluminum copper alloys (See Figure 103), or in thedetermination of the dispersion of lead in a leaded brass. For such applications, tungsten-target,beryllium-window tubes operating up to 50 kV are useful. The continuous spectrum from x-raydiffraction tubes can also be used. Microradiography has also been accomplished using the whiteradiation from ordinary radiographic tubes operated at a low voltage, although the x-ray intensityobtained at low voltages is severely limited by the thickness of the tube window.When segregation of components that do not differ greatly in atomic number must be detected,the use of the characteristic K x-ray spectrum from a suitable element gives the best results. Kcharacteristic radiation can be obtained by two methods. An x-ray tube with a target of thesuitable material has the advantage of a relatively high intensity of K radiation, but has thedisadvantage of requiring several x-ray tubes of different target materials or a tube withdemountable targets. In addition, a number of elements that emit K radiation that might be usefulcannot be made into x-ray tube targets. Use of K fluorescence radiation, obtained by irradiating asecondary target of a suitable material with the intense continuous spectrum of a tungsten-targettube avoids the disadvantage of the first method and gives a nearly pure K spectrum. However,the intensities available by this method are relatively low and long exposure times are needed.Extremely good contact between specimen and film is necessary if the maximum enlargement ofwhich the film is capable is to be achieved. Good contact can be obtained with a simplemechanical jig that presses the specimen against the film or plate, but best results are probablyobtained with a vacuum exposure holder. This consists of a plate with a milled recess into whichthe photographic material and specimen are placed and over which is put a flexible transparentcover. Evacuation of the recess with a vacuum pump or water aspirator causes the atmosphericpressure on the cover to press the specimen into intimate contact with the film or plate. (SeeFigure 104)Figure 104: Arrangement for microradiography using a vacuum exposure holder. Thespecimen thickness has been exaggerated for the sake of illustrative clarity.Any material placed between tube and specimen must be thin and of low atomic number (forexample, a thin sheet of cellulose derivative) to minimize x-ray absorption, and must have nomarked structure. Certain sheet plastic materials contain chlorine. These should not be used asRadiography in Modern Industry 165
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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
Page 113 and 114: soften considerably with prolonged
Page 115 and 116: Figure 77: The roller transport sys
Page 117 and 118: Rapid Access to Processed Radiograp
Page 119 and 120: Figure 78: Film-feeding procedures
Page 121 and 122: Chapter 11: Process ControlUsers of
Page 123 and 124: 3. Age of the developer replenisher
Page 125 and 126: Figure 80: Control chart below for
Page 127 and 128: DiscussionDensitometric data and pr
Page 129 and 130: 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: PhotofluorographyIn photofluorograp
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 and 184: Figure 113: A: Representation of a
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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