Dynamic Mechanical Properties Test And Discrete Elements Of Magnetite Concrete Value Simulation Study

Magnetite concrete is a kind of special concrete with shielding radiation functions,which is widely used in nuclear power,military,education,scientific research,medical treatment,and many other areas.The explosion of the terrorist event,as well as earthquake,tsunami,landslides and other impact load have been threatening the state,society and people’s life and property safety.So it’s particularly important to research the magnetite concrete under impact load of the structure dynamic performance.In this paper,Split Hopkinson Pressure Bar test(SHPB)and discrete element simulation are used to study the impact test of magnetite concrete.The main research contents are as follows:(1)The loading tests of magnetite concrete and ordinary concrete under static load and the tests of magnetite related materials are completed.Concrete specimens with the same strength grade were obtained.(2)The 100-mm-diameter Hopkinson pressure bar test device was used to conduct dynamic impact compression tests on magnetite concrete and ordinary concrete specimens under different impact velocities.And the original SHPB waveform,strain rate time history curve and stress-strain curve were obtained.Rubber,as waveform shaping material,which basically met the requirement of uniform stress condition inside the specimen and realized the approximate constant strain rate loading.(3)The influence of strain rate on dynamic stress-strain curve,limit strain,dynamic increase coefficient(DIF)and specimen failure characteristics of magnetite concrete was analyzed and compared with that of ordinary concrete under the same working condition.The test results show that both magnetite concrete and ordinary concrete are obviously rate-sensitive materials,and the strain rate sensitivity of magnetite concrete is lower than that of ordinary concrete.With the increase of strain rate,the compressive strength of magnetite concrete increases,but the ultimate compressive strength of magnetite concrete under the same strain rate is lower than that of ordinary concrete.The peak strain of magnetite concrete increases with the increasing strain rate.DIF is in good agreement with the strain rate relation and the standard recommended curve.The failure pattern of the specimen changed from the splitting damage at low strain rate to the massive crushing failure at high strain rate,and the average size of the fragments decreased with the increase of strain rate.(4)The discrete element software PFC2 D is used to carry out dynamic compressive simulation under different strain rates.The data obtained during the simulation test are compared with the mechanical characteristics and failure phenomena such as stress-strain curves in the experiment.The data are in good agreement,which shows that the meso-dynamic model established in this paper is reasonable and proves the feasibility of the discrete element PFC software in simulating the concrete process.At the same time,the micro-model is used to observe the crack distribution of the concrete failure mode.