A Study of the Relationship between Macroscopic Measures and Physical Processes Occurring during N00014-89-J-1708.
GEORGIA INST OF TECH ATLANTA MECHANICAL PROPERTIES RESEARCH LAB
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The principal experimental accomplishments during the second year of the program were two sets of x-ray tomographic microscopy XTM measurements on notched tensile samples. Fatigue crack growth was in a conventional servo- hydraulic machine before the samples were mounted in the in situ load frame. The choice of the extremely small by fracture mechanics standards samples was dictated by the need to have good sample transparency at the synchrotron x-ray energies with the highest fluxes typically up to about 25 keV before the flux starts to drop dramatically. A second consideration limiting the sample diameter is the number of detector elements and the maximum cross-sectional dimension of the sample a 10 mm diameter sample sampled with 10 to the third power detector elements yield a minimum pixel dimension of 10 um closure measurements requires pixels smaller than this.