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Observations and Analysis of Microcracks Produced in Dynamic Tension Tests of Concrete.
Final rept. 1 May 82-31 May 86,
SRI INTERNATIONAL MENLO PARK CA
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An important need in the study of dynamic tensile failure in concrete and brittle geologic materials is to characterize the failure process for a wide range of strain rates. The objective of this four-year research program was to develop and demonstrate experimental and analytical techniques to study the dynamic tensile failure of concrete at strain rates between 10s and 100s. The primary accomplishments of this program were 1 A new experimental method was developed to produce tensile failure in concrete in the presence of confining pressure at a strain rate of about 20s 2 A preliminary set of experiments was conducted to study the unconfined and confined tensile failure of concrete at a strain rate of about 20s 3 These experiments were interpreted with numerical calculations to estimate the dynamic strength enhancement, the apparent strain-softening behavior of the concrete, and the extent of damage in the specimens 4 A technique was developed to observe the microcrack damage in the tensile specimens microcracks were charted for a concrete specimen after a dynamic tension experiment 5 Analyses of microcrack growth showed that crack propagation velocity may be the source of the tensile strength enhancement observed in the dynamic tension experiments.
APPROVED FOR PUBLIC RELEASE