Recent years have seen significant advances in both low and high energy X-ray microscopy. The image in X-ray microscopy is usually formed by differences in absorption of X-ray photons. Soft X-ray microscopy (energies below a few thousand eV) uses wavelengths under 10 nm. Since light wavelengths are approximately 500 nm, resolution is much better with X-rays. One can obtain nanoscale resolution with focused soft X-ray imaging of thin biological objects. To achieve high spatial resolution in high energy X-ray microscopy one can use focused parallel monochromatic beams produced by synchrotron radiation or one can use a microfocal X-ray source with high geometrical magnification of the image. For weakly absorbing objects the image contrast can be enhanced by X-ray refraction on inhomogeneities and phase contrast formation. The physical principles of the phase contrast technique are similar to those in optics and are based on X-ray interference. Modeling and experimental aspects of the phase contrast technique with a microfocal X-ray source and the effects of geometrical and material parameters are reviewed in some detail. Examples of phase contrast of porosity in a polymer layer and an aluminum weld are shown. The computer-simulated images are compared with images from experiment with a 5 μm microfocal X-ray source. Phase retrieval methods and phase map reconstruction from measured X-ray images are also discussed. Applications of the phase-contrast X-ray imaging include medical radiology, material science, and industrial radiography and tomography.
Microradiographic and ultrasonic characterization of fatigue crack emanating from pitting corrosion is discussed. Crack initiation and growth from the artificial pit of different depths in Al-2024-T3 alloy is studied experimentally. The effect of crack closure on the radiographical and ultrasonic detection of fatigue crack is also illustrated. The experimental results were analyzed using fracture mechanics models including those for small cracks. The model shows very good agreement with experiment in describing the initial and growth of a crack emanating from a pit and in predicting the dependence of the reduction of fatigue life on pit size. Using this analysis, a relation between the depth of the corrosion pit and the fatigue life is established, and thus the prediction of fatigue life of the sample with corrosion pit can be predicted based on the radiographic and ultrasonic measurements of pit and crack sizes.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.