Mechanism on enhancement of dynamic flexural tensile strength for nonuniform brittle materials under impact loading
PAN Feng1，DANG Faning1，JIAO Kai1，2，SHI Junping1
(1. Institute of Geotechnical Engineering，Xi'an University of Technology，Xi'an，Shaanxi 710048，China； 2. Sinohydro Bureau 3. Co.，Ltd.，Xi'an，Shaanxi 710016，China)
Abstract：This paper dealt with the dynamic strength enhancement mechanism of rock-concrete-like nonuniform brittle materials. The theoretical analysis of failure morphology of the specially designed three-point bending beam was made under different loading rates，and putted forward the root of dynamic strength enhancement as results of the combined effect of materials inhomogeneity and inertia force，and held that the static and dynamic strengths of this kind of material were related with the crack path at failure. When in static loading，the cracks of concrete growing through the thin-weak interface of the material，so that it needed minimum energy at material failure. Under the action of dynamic loading，the cracks of concrete developed along the shortest pathway in such a way that cracks can cut parts of aggregates，and the energy needed for material failure was raised correspondingly，the contribution of materials inhomogeneity to the enhancement of dynamic strength had emerged，the inertial effect remarkably increased with the increasing of loading rate. When the loading rate exceeded a critical value，the dynamic strength caused by materials inhomogeneity would not increase，thereby，only the contribution of inertial effect played a role in the dynamic strength enhancement. The theory proposed in this paper was verified by means of the specially designed quasi-static loading test and different loading rates impact test for nonuniform brittle materials three-point bending beam，and the results were basically in accordance with the theoretical assumption.
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2015, Vol. 34 
