Controlled slow-speed microcutting tests were made on single crystal silicon. Micro-Raman spectroscopy confirmed the presence of amorphous silicon within the microcutting grooves as well as in the debris particles removed from the grooves. These results indicate that pressure-induced transformation to metallic silicon can occur during microcutting and the ductile metallic phase will facilitate the cutting process. Raman spectroscopy further indicated the presence of large residual tensile strains in some areas of the microcutting grooves.
Biaxial creep behaviors of stress-relieved and recrystallized thin-walled tubing of Ti-3AI-2.SV and Zircaloy-4 are considered under equal hoop and axial stresses by internal pressurization superimposed with axial load. Both hoop and axial strains were monitored and the ratio of the strain rate along the hoop to that along the axial directions is considered to represent the degree of anisotropy.In both of these alloys, relatively weak hoop direction in cold-worked stress-relieved (CWSR) materials became slightly stronger following recrystallization. Crystallographic texture was considered in terms of x-ray pole figures from which the crystallite orientation distribution functions (CODFs) were derived and crystal plasticity model with slip dominant on prism planes was combined with the CODFs to predict the creep anisotropy. While good correlation was noted for recrystallized materials, distinct deviations are observed for CWSR that are believed to arise from grain shape anisotropy. The relatively small (equiaxed) grain size along the hoop and radial directions results in grain boundary sliding leading to stress enhancements along these directions. This anisotropy in grain boundary sliding is shown to explain the observed deviations.
Acoustic emission measurements were made during controlled indentation of soda-lime glass. Pulses were detected at specific points during the loading or unloading cycles. The response and reproducibility were dependent upon the indenter shape. Comparison with earlier data reported in the literature showed that the acoustic activity was correlated with crack initiation events corresponding to median/ radial, lateral, or other fracture modes.
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