混凝土直切槽平台巴西圆盘冲击劈裂拉伸断裂特性试验和数值模拟研究

Tests and numerical simulation for splitting tensile fracture properties of CSTFBD concrete specimen under impact loading

采用变截面霍普金森压杆(SHPB),对高速冲击荷载下混凝土的断裂特性和裂纹演化进程进行了研究。对含复合型裂纹直切槽平台巴西圆盘(CSTFBD)进行劈裂拉伸试验,并结合理论研究了不同水灰比、不同应变率、不同预设裂纹长度和倾角对裂纹分布及断裂韧性的影响;采用扩展有限单元法(XFEM)模拟了具有不同预设裂纹倾角试件的开裂进程,得出开裂过程中试件内部的应力分布情况。结果表明,复合断裂韧性比对预制裂纹倾角的变化敏感,与裂纹长度和倾角呈负相关,而与应变率无关;次生裂纹的开裂并非发生在预设裂尖处,且裂纹倾角越大,裂尖应力集中越小、主裂纹发展越缓慢。

Here,a split Hopkinson pressure bar(SHPB)was adopted to investigate fracture features and crack evolution process of concrete specimens under high speed impact loads.Dynamic splitting tensile tests were conducted for cracked straight-though flattened Brazilian disc(CSTFBD)with mixed mode pre-cracks,and effects of water-cement ratio,strain rate,pre-crack length and inclination on crack distribution and fracture toughness were theoretically studied.The extended finite element method(XFEM)was adopted to simulate crack cracking process of specimens with different pre-crack inclinations,and obtain stress distribution inside specimens.The results indicated that the compound fracture toughness ratio is sensitive to variation of pre-crack inclination,and negatively correlated to crack length and inclination,but not related to strain rate;secondary crack cracking does not happen at preset crack tip,the larger the crack inclination,the smaller the stress concentration at crack tip and the slower the main crack propagation.