Research On The Inertial Effect Of Concrete-like Materials In Hopkinson Experiments

The structure made by the concrete-like materilal should be designed to meet the static loading requirements and resist the dynamic impact loading.The inertial effect and real rate effect are the main effects that should be considered in the dynamic experiments to concrete-like materials under intermediate and high strain rate.The real rate effect is the genuine dynamic response of the material,which becomes the core content in the dynamic tests.However,the premise to determine the genuine dynamic response of concrete-like materials is that the inertial effect should be understood clearly.Combined with the existing studies,this paper mainly makes further analysis to the inertial effect in the dynamic compressive and tensile testing of concrete-like materials,including the following several aspects:(1)The research on the mechanism of inertial effect and its influencing factors in the dynamic compressive testing of concrete.At present,lots of research results indicate that the inertial effect is the key factor that enhances the measured dynamic compressive strength(higher than the real dynamic compressive strength).Based on the numerical simulation analysis method,this papaer conducts the concrete SHPB simulation to reveal the influencing factors and mechanism of the inertial effect.It is found that the existing inertial formulas do not apply to the dynamic compressive experiment of the concrete.Moreover,the study to the mechanism of the inertial effect and the analysis to the influencing factors are further carried out in the numerical simulation.(2)The analysis to the inertial effect in the dynamic tensile testing of concrete.So far,researchers have not reached an agreement with the influence of inertial effect in the dynamic tensile testing of concrete.Therefore,this paper systematically conducts the three dynamic tensile experiments(viz,the dynamic direct tension testing,the dynamic splitting testing,the dynamic spalling testing)and the numerical simulations based on these tensile testings.Finally,the phonomenon that the inertial effect has different influence in the dynamic compressive and tensile testing is explained through the Poisson effect and the radial constraints induced by the inertia.(3)The numerical simulations to the tubular specimen of concrete-like materials.The numerical results indicate that the radial stress of specimen increase with the loading and the inertial effect really exists in the dynamic tensile testing of concrete-like material.However,through the comparison among the numerical results of different inner diameter tubular specimens,it is found that the trends that dynamic stresses of different diameter tubular specimens increase with the loading are almost consistent with each other,which means that the inertial effcect has little influence in the dynamic tensile experiments.(4)The study to the quasi-static tensile testings of concrete-like materials.Compared with other materials,the available experimental data in the direct tensile experiments of concrete-like materials are less,especially to the mortar.The tubular specimen used to investigate the influence of inertial effect in the dynamic tensile experiment should be fabricated by the plain concrete(mortar).Besides,the quasi-static tensile testing is the basis of dynamic analysis.Therefore,this paper conducts the splitting testing and the dumbbell specimen design for the direct tension in order to provide a effective way to measure the static tensile property of mortar.(5)The dynamic simulation to the dumbbell specimen of concrete-like materials.The success rate of concrete-like materials specimen in dynamic direct tensile testing is not high.Therefore,the numerical simulation to the different dumbbell specimens of concrete-like material is conducted to search for the optimal form of concrete-like materials dumbbell specimen in the dynamic direct tensile testing.Meanwhile,through the comparison of different dumbbell specimens in the numerical models,the variable of inertial effect also can be introduced to analyze the influence of inertial effect to the results.When the optimal design on the dumbbell specimen is studied,the influence of inertial effect to the dynamic direct tensile strength of concrete-like materials is also further investigated.