混凝土SHPB试验端面摩擦效应研究

Study on concrete SHPB tests with interface friction effects

分离式霍普金森压杆(split Hopkinson pressure bar,简称SHPB)试验是测量材料在高应变率下动态特性的常用试验方法.基于LS-DYNA对混凝土的SHPB试验进行数值模拟,其中混凝土采用K&C模型,利用SHPB二波法理论重构了抗压状态下混凝土试件的应力应变曲线,通过对比模拟结果和试验结论,分析了混凝土试件在动态荷载作用下的破坏规律,并通过设置不同的混凝土与SHPB杆件界面摩擦因数μ,将界面摩擦效应对混凝土动态抗压强度的影响进行了量化分析.研究结果表明:随着应变率的上升混凝土动态抗压强度增加且混凝土损伤演化更充分,动力增强因子(dynamic increasing factor,简称DIF)随着μ的增加而增加,但当μ每增加0.1时,DIF的增加幅度将会下降5%左右,且端面摩擦效应对DIF影响的最大值约为60%.

Split Hopkinson pressure bar（SHPB）tests are the most popular experimental techniques used for dynamic characterization of various materials under high strain rates.A series of SHPB numerical tests were conducted based on LS-DYNA,and KC local concrete damage model was used for modelling concrete.The stress-strain curves of the concrete specimens are reconstructed with the two-wave theory.The failure rules of concrete specimen under dynamic load are analyzed by comparing the simulation results and the test results.Furthermore,the effect of interface friction on the dynamic strength of the concrete was analyzed based on different SHPB interface friction coefficients.The results show that with the increase of strain rate,the dynamic compressive strength of concrete increases and the damage evolution of concrete is more sufficient.As the friction coefficient rises,the dynamic increasing factor（DIF）increases.While the friction coefficient increases by 0.1,there is about5% decrease in DIF increments.Considering the effect of interface friction on DIF,the increment of DIF is about60% mostly.