Micromechanics and Constitutive Modeling og Granular Materials in Stress Reversal and Cyclic Loading Locaized Deformation: Experimental Observation and Modeling.
Final rept. 1 Feb-30 Sep 95,
CALIFORNIA UNIV SAN DIEGO LA JOLLA CENTER OF EXCELLENCE FOR ADVANCED MATERIAL S
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The work performed under this grant, focused on the process of initiation and growth of shear bands in frictional granules. Such localized deformations commonly occur in particulate media and are of considerable engineering and scientific importance. They occur in a variety of areas of advanced materials processing, at different scales. They are a common mode of failure in soil masses and geological formations. A technique has been developed to study the deformation of lead doped lines of granules within the sample of a granular material, using the UCSD 5 large hollow cylindrical cell, together with flash X ray photography. The special cell has been modified for this purpose, and several successful tests have been performed. The facilities are then employed to develop in depth fundamental understanding of the microstructure of a shearband zone, and the spatial variation of the accompanying deformation. With this technique, we have captured the deformation that leads to shearband formation in several preliminary experiments. We have successfully solidified the sample containing shearbands, in situ. using a polymeric resin. We have then prepared sections for complete microstructural analysis, and have performed some preliminary analysis of the results. These and related issues are discussed in this report.