基于改进型SHPB的混凝土动力冲击研究

Research on dynamic impact of concrete based on improved SHPB

混凝土作为一种重要的建筑材料,其抗冲击性能关乎核电站、大坝、机库等重要结构设施的安全稳定。在动力侵彻过程中,混凝土材料内部赋存大量随机分布的微孔隙、裂隙等被激活、扩展,诱使混凝土发生宏观破坏,研究混凝土材料破坏过程中的动态破碎机理及能量消耗可直观反映材料的防护性能。笔者提出了一种基于弹体侵彻理论的改进型分离式霍普金森压杆(SHPB)动载冲击试验方法,在入射杆端部设计安装锥度为120°的圆锥形冲头,对常规混凝土、RGC(橡胶混凝土)和SFRC(钢纤维混凝土)进行动力冲击研究。通过分析改进型SHPB系统上应力波透反射效应,获得含不同掺合料混凝土试块的宏观破坏形态、破碎产物粒径分布规律和能量耗散规律。试验结果表明:RGC试块和常规混凝土破坏模式相似,宏观破裂成几个大块度试块,而SRFC在钢纤维“桥连”作用下,呈“微裂而不散,裂而不断”的破坏模式;在相同子弹冲击速度下,试块块度粒径SRFC最大、RGC次之、常规混凝土最小,表现出抗破碎能力:SRFC>RGC>常规混凝土;随入射能量的增加,材料破碎能耗均呈线性增加,其中SFRC增长分别是RGC、常规混凝土的1.074、1.49倍。

As an important building material,concrete's impact resistance is related to the safety and stability of important structural facilities such as nuclear power plants,dams,and hangars.In the process of dynamic penetration,a large number of randomly distributed micropores,cracks,etc.are activated and expanded in the concrete material,which induces the macroscopic damage of the concrete.The study of the dynamic crushing mechanism and energy consumption during the failure process of the concrete material can directly reflect the material.The protective performance.An improved split Hopkinson pressure bar(SHPB)dynamic impact test method based on the theory of projectile penetration is proposed.A conical punch with a taper of 120°is designed and installed at the end of the incident bar to conduct dynamic impact research on conventional concrete,RGC(rubber concrete)and SFRC(steel fiber concrete).By analyzing the transmission and reflection effects of stress waves on the improved SHPB system,the macroscopic failure morphology,particle size distribution and energy dissipation of concrete test blocks with different admixtures were obtained.Test results:The failure mode of the RGC test block is similar to that of conventional concrete,macroscopically broken into several large-scale test blocks,while the SRFC under the action of the steel fiber"bridging"shows"micro-cracking but not disintegrating,but continuous cracking."Under the same bullet impact velocity,the block size of SRFC is the largest,RGC is the second,and conventional concrete is the smallest,showing the resistance to crushing:SRFC>RGC>conventional concrete;With the increase of energy,the energy consumption of material crushing increased linearly,and the increase of SFRC was 1.074 times and 1.49 times that of RGC and conventional concrete,respectively.