Radiographic Geometric Unsharpness

Radiographic NDT method

Don't forget these important points when calculating the Ug Factor........

Ug = F (t / d)


Ug (unsharpness due to geometry)
= F(focal spot size - cross dia.) X (top-of-specimen to film distance / distance - measure from the source to the top-of-specimen)

1.  The trick is to remember measuring to-and-from the top-side of the specimen for the t / d. If this is a thick piece, the difference can be great from a thin section..........this is what we are limiting........right?

2.  Don't forget to use the same measuring UNITS for all calculations. (inches or mm, etc.)

3.  Maximum Geometric Unsharpness:

Material Thickness
Under 2 in. (50mm) = max. Ug. 0.020in (0.50mm)
2 in. through 3 in. (50 - 75mm) = max. Ug. 0.030in (0.75mm)
Over 3 in. - 4 in. (75 - 100mm) = max. Ug. 0.040in (1.00mm)
Over 4 in. (100mm) = 0.070in. (1.75mm)  



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