Figure 6-24. Nomogram to Assist in Solving Equation U g = Ft/d

Figure 6-23. Possible Geometric Distortions.

TM-1-1500-335-23 Nondestructive Inspection Methods Manual
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T.O. 33B-1-1 6-54 conditions. An example of its use follows, but note that 3 out of 4 terms in the equation must be known before it can be used. Figure 6-24. Nomogram to Assist in Solving Equation U g = Ft/d. 6.7.2.5.2 Suppose that a specimen having a maximum thickness of 1.5-inch (t) is to be radiographed at 20-inch source-to-film distance (d) using a source of effective focal size 6mm. The need is to establish an approximate value for U g . The steps in using the nomogram are: a. Plot the points A and C that represent the known value of F and t. The pivot line is intersected at B. b. Plot a line joining point D (the value of d) and B. The extension of this line at E gives the value of U g (0.47mm). 6.7.2.5.3 It should be remembered that unsharpness of the radiographic image is also affected by the characteristics of the X-ray film. Therefore, the total image sharpness may be controlled by either geometrical unsharpness or film unsharpness. Whichever unsharpness value is the greater will control the total image unsharpness. In a given situation, the

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