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Articles you may be interested inThe load separation criterion in elastic-plastic fracture mechanics: Rate and temperature dependence of the material plastic deformation function in an ABS resin AIP Conf.

Applied and residual lattice strains were determined by neutron diffraction during a tensile test of a weakly textured austenitic stainless steel and were compared to the predictions of a self-consistent polycrystal deformation model. Parallel to the tensile axis the model predictions are generally within the resolution of the diffraction measurements, but perpendicular to the tensile axis discrepancies are noted. Discrepancies between model and measurements were greater for the residual lattice strains than during loading. It is postulated that this is because the model does not predict reverse plasticity during unload.

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The structures of ordered and disordered ␤-eucryptite have been determined from Rietveld analysis of powder synchrotron x-ray and neutron diffraction data over a temperature range of 20 to 873 K. On heating, both materials show an expansion within the (001) plane and a contraction along the c axis. However, the anisotropic character of the thermal behavior of ordered ␤-eucryptite is much more pronounced than that of the disordered compound; the linear expansion coefficients of the ordered and disordered phases are ␣ a ‫ס‬ 7.26 × 10 −6 K −1 ; ␣ c ‫ס‬ −16.35 × 10 −6 K −1 , and ␣ a ‫ס‬ 5.98 × 10 −6 K −1 ; ␣ c ‫ס‬ −3.82 × 10 −6 K −1 , respectively. The thermal behavior of ␤-eucryptite can be attributed to three interdependent processes that all cause an increase in a but a decrease in c with increasing temperature: (i) Si/Al tetrahedral deformation, (ii) Li positional disordering, and (iii) tetrahedral tilting. Because disordered ␤-eucryptite does not exhibit tetrahedral tilting, the absolute values of its axial thermal coefficients are smaller than those for the ordered sample. At low temperatures, both ordered and disordered ␤-eucryptite exhibit a continuous expansion parallel to the c axis with decreasing temperature, whereas a remains approximately unchanged. Our difference Fourier synthesis reveals localization of Li ions below room temperature, and we suggest that repulsion between Li and Al/Si inhibits contraction along the a axes.

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