August 1, 2015.
X-rays are widely used in medicine and materials science to identify impurities or fractures within the target object. In material science, x-rays can be used to identify the thickness of samples with different material densities. The current method is to collect a radiograph using estimated conditions, evaluate the results, then make changes to the conditions. The residual image can be rescanned making it possible to obtain an image of lower radiographic density. By tabulating or graphing the effects of energy changes and rescans, a more informed choice of conditions is possible.
For this study, six materials were chosen with a material density ranging from 1.74-16.65 g/cc. During each experiment, different voltages are used and several rescans are taken if the residual image on the film plate was not erased.
When comparing the rescans, the largest drop in radiographic density occurred between the original scan and the first rescan. The relative amount of radiographic density decreased is lower after each scan. The percent change in radiographic density between rescans ranged from 4-12% overall. As the material density or thickness increased, the data consistently showed the radiographic density decreased. The denser, thicker materials may only need a few rescans at the higher voltages, and less dense, thinner materials may need more. The change in voltage showed a similar trend as that of the rescans. The voltages used in this experiment were too high for most of the materials and thicknesses, but some general trends were observed.
Materials Science and Engineering
California Polytechnic State University (Cal Poly SLO)
This material is based upon work supported by the Chevron Corporation and is made possible with contributions from the National Science Foundation under Grant No. 1340110, Howard Hughes Medical Institute, S.D. Bechtel Jr. Foundation, National Marine Sanctuary Foundation, and from the host research center. Any opinions, findings, and conclusions or recommendations expressed in this material are solely those of the authors. The STAR Program is administered by the Cal Poly Center for Excellence in STEM Education on behalf of the California State University system.