UHPFRC圆盘动态劈裂试验及基于μXCT图像的破坏机理研究  

Dynamic split tests of UHPFRC discs and failure mechanism analysis based onμXCT images

作　　者：姚勇 杨贞军 张昕 庞苗[1] 李雅祺 喻渴来 YAO Yong;YANG Zhenjun;ZHANG Xin;PANG Miao;LI Yaqi;YU Kelai(College of Engineering and Architecture,Zhejiang University,Hangzhou 310058,Zhejiang,China;Hubei Provincial Key Laboratory of Geotechnical and Structural Safety,School of Civil Engineering,Wuhan University,Wuhan 433000,Hubei,China)

机构地区：[1]浙江大学建筑工程学院,浙江杭州310058 [2]武汉大学土木建筑工程学院湖北省岩土与结构安全重点实验室,湖北武汉433000

出　　处：《爆炸与冲击》2023年第5期68-85,共18页Explosion and Shock Waves

基　　金：国家自然科学基金(52173300,51974202);湖北省重点研发计划(2020BAB052)。

摘　　要：采用分离式霍普金森压杆对钢纤维体积分数为0~3%的超高性能纤维增强混凝土(ultra high performance fibre reinforced concrete, UHPFRC)圆盘试件进行应变率为1.72~7.42 s^(-1)的动态劈裂试验,使用高速摄像机结合数字图像相关(digital image correlation, DIC)法获得试件表面裂缝扩展全过程图像和应变演化过程,并对冲击前后试件进行微观X射线计算断层扫描(micro X-ray computed tomography,μXCT),获得分辨率为56.7μm的三维内部图像,并进行统计和破坏机理分析。结果表明:(1)相比无纤维试件,掺入1%~3%的钢纤维,静、动劈裂强度分别提高84%~131%和47%~87%,动劈裂强度增强因子(即动静强度比值)为1.07~1.72;(2) DIC应变图像分析表明,无纤维试件裂缝集中、破坏快、能耗低;含纤维试件裂缝弥散程度大、能耗高、延性好,且随着纤维含量的提高而提升;(3)μXCT图像分析表明,试件中钢纤维体积分数为1.04%~2.47%,与设计基本一致,孔洞体积分数为0.98%~1.71%,纤维掺量的提高,降低了孔洞数量和总体积分数,但孔洞的平均体积和平均等效直径增大;裂缝桥连纤维数量的增加,减小了主裂缝的体积和平均宽度,提高了裂缝面的粗糙度和相对表面积,从而提高了试件的强度、能耗、韧性和延性。In order to better investigate the dynamic tensile properties and damage mechanism of ultra-high performance fibre reinforced concrete(UHPFRC),dynamic split tests with the strain rates of 1.72-7.42 s^(-1) were carried out by a split Hopkinson pressure bar for UHPFRC discs with the fibre volume fractions of 0-3%.The surface crack propagation processes of the UHPFRC discs were captured by a high-speed camera and the images were analyzed by the digital image correlation(DIC)technique for strain evolution.Micro X-ray computed tomography(μXCT)scanning of the UHPFRC disc specimens before and after the dynamic tests was also conducted.The 3D images of the internal micro structures of the specimens with a voxel resolution of 56.7μm were reconstructed,and they were then processed to statistically quantify the distribution,volume fractions and sizes of pores,fibres and cracks.Moreover,the dynamic failure mechanisms,such as pullout from the matrix,bending and breakage of steel fibres,crack propagation and merging in the mortar,etc.,were visualized and analyzed.The main results obtained are as follows.(1)The addition of 1%-3%steel fibres raises the static and dynamic splitting strength by 84%-131%and 47%-87%,respectively.The dynamic increase factor(ratio of dynamic to static strength)is 1.07-1.72.(2)DIC images demonstrate that the fibres lead to more dispersed cracks,slower crack propagation,higher energy consumption and higher ductility.(3)TheμXCT image analysis shows that the fibre volume fraction is 1.04%-2.47%,consistent with the designed proportion,while the porosity is 0.98%-1.71%.Fibres reduce the porosity and the number of pores,but increase their average volume and equivalent diameter.The increase of crack-bridging fibres reduces the volume and width of main cracks and raises the surface roughness and the relative surface area of cracks,resulting in the increase of strength,energy dissipation,toughness and ductility of specimens.The research data are useful for improvement of dynamic design guidelines and optimiz

关 键 词：动态劈裂 超高性能纤维增强混凝土 微观X射线计算断层扫描 断裂机理 数字图像相关 

分 类 号：O347.3[理学—固体力学]