Investigations on dynamic failure behaviors and energy transfer efficiency of heat-treated high-performance concrete under multiaxial constraints

Abstract

In order to explore the internal relationship between the energy transfer efficiency and the dynamic mechanical response of thermal damage concrete under the coupling action of multi-axial stress constraint and high strain rate, the dynamic compression test of high performance concrete is carried out by using the true triaxial Hopkinson pressure bar test system and the combined effects of high temperature, multi-axial stress constraint and impact velocity are fully considered. The temperature effect and strain rate effect of the dynamic failure mechanical behavior of concrete under biaxial stress constraint are analyzed, and the influence mechanism of temperature, prestress and impact velocity on the energy transfer efficiency of the failure process of concrete samples is discussed. The research results show that the dynamic strength of concrete under biaxial stress constraint has both the strengthening effect of loading rate and the hardening and weakening effect of temperature. The dynamic failure of concrete subjected to different degrees of thermal damage under biaxial stress constraint changes from brittleness to plasticity (with 300 °C as the turning point). Under the biaxial stress constraint, the energy absorptivity and reflectivity decrease with the increase of the intermediate principal stress, while the transmittivity shows the opposite trend. When the biaxial stress constraint state is changed to true triaxial constraint state, the energy transfer efficiency changes abruptly along the original evolution trend. The sensitivity of high temperature and stress constraint on the energy transfer efficiency of concrete during dynamic compression is more significant than that of impact velocity. The effects of temperature and stress constraint state (change of intermediate principal stress) on energy dissipation density are positively correlated. The energy dissipation density has an exponential function growth relationship with the dynamic strength and a linear growth relationship with the strain rate.