Numerical Simulation Of Semir-circular Bending Test For Concrete Under Quasi-static And Dynamic Loading Conditions

In this paper, the static and dynamic concrete bending experiments weresimulated to research mechanical behaviors under the different static and dynamicforce equilibrium conditions, and the correlate formulas was fitted.First of all, finite element program was used in the numerical simulations ofsemi-circular bending (SCB) test for the sample with different Poisson ratios,loading widths and different L/D ratio under static force equilibrium conditions.The effects of the Poisson ratio, loading width and different L/D ratio wasanalyed, the related laws were found out and the related formula was fitted.Compared with other scholars’ researches, these models adds a round bar pad usedin real experiments, and the load was applied by the way of contacting, so thewhole simulation process are closer to the real experiments, then the more realisticsimulated data can be obtained, and the fitting formula is more accurate.Secondly, Ls-Dyna program was used in the numerical simulation ofsemi-circular bending (SCB) test loaded by the split Hopkinson pressure bar (SHPB)device under the high strain rate with the dynamic force equilibrium condition. Thesimulation results show that, compared with the Brazilian disk (BD) test, the SCBtest has obvious advantages for measuring the dynamic indirect tensile strength ofbrittle materials. First of all, the influence of the dynamic force equilibrium processof the specimen on the experimental accuracy is less under the condition ofdifferent incident wave shapes. It mainly displays in two aspects:1) The point ofmaximum tensile stress has a fixed position;2) The calculation method ofmaximum tensile stress based on static elastic theory has higher precision.Secondly, the SCB test can increase the ratio of the maximum tensile stress tomaximum compressive stress, so the brittle materials can occur tensile failureeasily. The simulation results also show that:1) In the SCB test, the three-wavemethod is not suitable to calculate the maximum tensile stress of specimen and thetransmitted wave should be directly used to calculate.2) The round bar strip at thetop of the specimen can cause a certain degree of stress concentration, in place ofthe arc-shaped cushion used in the BD test can solve the problem effectively.In addition, since the SCB experiment sample points for complex stress state,therefore in the experiment to ensure the realization of tensile failure is a measureof the effectiveness of important factors. The brittle material commonly usedGriffith strength theory are analyzed, and according to the theoretical calculation,equivalent stress, verify the dynamic SCB experimental validity.In addition, the SCB experiment sample points has complex stress state, sothat ensuring the realization of tensile failure in the experiment is a measure of theeffectiveness of important factors. Griffith strength theory commonly used for thebrittle material was used to analyse and calculate the equivalent stress. Thedynamic SCB experimental validity was also verified.