Numerical Simulation Of Split Hopkinson Pressure Bar Test For Rubber Modified Concrete

China ranks among the worlds’ major junked tire producers.The application of these junked tires to road construction will help improve the flexibility of road,strengthen its high-temperature resistance,strengthen concrete’ impact resistance,and defer the road aging.In this way,the road service life can be extended,and meanwhile,noises from cars can be reduced.This is an effective way to turn the junked tires,known as "black pollution",into gratifying "black gold".This paper established SHPB test finite element model of rubber-modified concrete in the LS-DYNA template of HyperMesh,and exported the solving files.Then the files were submitted to the LS-DYNA3D for solving computation.Finally,the changing process and stress nephogram caused by the impact load on the rubber concrete was observed in HyperViev.At the same time,the strain-time curve and stress-time curve of the incident wave,transmitted wave and reflected wave were exported with HyperGraph.What’s more,"two-wave method" was applied to reconstruct the stress-strain curve of rubber concrete.Mainly the following items were involved:(1)SHPB test model of rubber concrete was simplified;the appropriate size of SHPB devices was determined;the distribution scheme of rubber particles in concretes was finalized.(2)Viewed from the perspective of the selection of unit type,hourglass control,and contact type and of contact computation,the reliability of SHPB test finite element simulation of rubber concrete was probed into.(3)Studies were conducted on the effect of pulse shape(triangle wave,trapezoidal wave and rectangular wave),pressure-lever diameter(φ37mm,φ74mm and φ100mm)and the stress pulse amplitude on the geometric dispersion phenomena of the pressure lever’s medium-wave propagation process.According to the simulation results,the greater the lever diameter was,the more obvious the dispersion effect became.The greater the stress pulse amplitude was,the more obvious the dispersion of rectangular wave became.The influence of the amplitude on the dispersion of triangle wave and trapezoidal wave is small.Performing perfectly in dealing with the dispersion effect caused by the wave’s propagation in the pressure lever,triangle wave achieved the best results,followed by trapezoidal wave.The rectangular wave featured the most obvious dispersion effect.(4)By computing stress balancing factors,studies were conducted on the effect of pulse shape(triangle wave,trapezoidal wave and rectangular wave)and the length-diameter ratio(0.5,1.0,and 1.5)of test pieces on the early-phase stress unevenness of test pieces.The simulation results showed that with the increase of length to diameter ratio,the specimen to achieve stress uniform need more time.The application of triangle wave and the trapezoidal wave with a certain uptrend basically met the stress evenness assumption of SHPB test.(5)By loading triangle-wave velocity pulse with peak velocity of 4m/s,6m/s and 8m/s respectively,numerical simulation of SHPB test on rubber-modified concrete(RC)was conducted,with stress-strain curve of different test pieces obtained.Besides,analysis was made of the effect of rubber powder(Particle size with 1mm,2mm,3mm;volume fraction with 10%,20%,30%and 40%)on the dynamic compressive strength of rubber-modified concrete,and of the strain-rate enhancement effect.And meanwhile,analysis was made of the effect of rubber powder on the deformation performance of RC.