爆破冲击荷载作用下宏观孔隙混凝土损伤演化的近场动力学模拟

Peridynamic Simulation of Damage Evolution of Macro-porous Concrete Under Blasting Load

针对静载、冲击荷载条件下宏观孔隙混凝土的孔隙参数对混凝土损伤演化过程的影响问题,采用MATLAB程序结合蒙特卡罗方法生成随机的孔隙结构物理模型,通过自编近场动力学程序模拟了单轴压缩下宏观孔隙混凝土的应力应变过程,并制备了以聚苯乙烯小球高温融化为孔隙体的混凝土砂浆试件,对宏观孔隙率0%~40%的混凝土试件进行了单轴压缩,实验验证了模型计算结果的准确性,随后模拟了爆破冲击作用下宏观孔隙混凝土的裂纹萌发与扩展。结果表明:孔隙率对宏观孔隙混凝土材料力学性能的影响显著,随着孔隙率的增加,试样的密度、抗压强度、弹性模量以及纵波波速不断降低,当孔隙率达到30%后,孔隙率对轴线抗压强度影响减弱,并且出现峰前应力跌落现象。孔隙率为零的混凝土试样在无围压冲击荷载作用下具有明显的压剪破坏形式,而含孔隙的混凝土由于大量的孔隙存在导致孔隙间混凝土骨架的拉伸或剪切贯通破坏。在相同冲击荷载下不同孔隙率混凝土的破坏情况不同,孔隙率大的孔隙混凝土试样破坏严重,表明孔隙率对冲击载荷作用下混凝土试件能量耗散起着重要作用。

For study the influence of macro-pore parameters on the damage evolution of concrete under static and impact loads,a physical model of random pore structure was generated by MATLAB program based on Monte Carlo method,and the stress-strain process of macro porous concrete under uniaxial compression was simulated by a self-programed peridynamic program.Furthermore,the accuracy of the calculation results was verified by uniaxial compression experiments of concrete specimens with macro porosity of 0%~40%.The concrete mortar specimens were prepared with polystyrene spheres which melt at high temperature into voids.Finally,the crack germination and expansion of the macro porous concrete under blasting impact loads were simulated.The results show that the porosity has a significant effect on the mechanical properties of macro porous concrete materials.With the increase of porosity,the density,compressive strength,elastic modulus and longitudinal wave velocity of samples continuously decreases,respectively.When the porosity reaches 30%,the effect of porosity on the axial compressive strength is weakened,and the stress before the peak has a drop phenomenon.The concrete samples with zero porosity have obvious compression shear failure mode under the impact load without confining pressure,while the existence of a large number of pores leads to tensile or shear failure of concrete skeleton.Under the same impact load,the failure of concrete with large porosity is more severe,which indicates that porosity plays an important role in energy dissipation of concrete under impact load.