大直径SHTB实验装置数值模拟及混凝土细观骨料模型动态直拉研究

对混凝土材料在高应变率下的动态拉伸实验多以劈裂和层裂的形式进行，然而它们作为间接研究混凝土动态拉伸性能的实验技术具有一定的局限性，亟需使用大直径分离式Hopkinson拉杆（split Hopkinson tensile bar，SHTB）设备对混凝土进行动态直拉实验。因此，运用数值模拟方法对一种新型的霍普金森拉杆的入射波进行了研究，并对设备的局部构件进行改进，使其不仅具有对混凝土试件的胶粘连接方式，也可通过螺纹连接配套夹具以同时兼顾挂接等其他连接方式。针对改进后的SHTB装置，建立了圆环状三维混凝土细观骨料模型。通过数值模拟与实验结果的对比，验证了采用空心圆管式SHTB装置的有效性，并为混凝土细观骨料模型的动态拉伸模拟提供了思路。

Numerical simulation on a large diameter SHTB apparatus and dynamic tensile responses of concrete based on mesoscopic models

Research of concrete materials subjected to tensile stress wave at high strain rates is currently based on splitting experiments and spalling experiments with a split Hopkinson pressure bar device, however, they are not appropriate to study the stress-strain relationship of concrete materials subjected to one dimensional tensile stress wave. Therefore, the large diameter split Hopkinson tensile bar (SHTB) is urgently needed to perform direct dynamic tensile study of concrete materials. Mechanical analysis of a new type of SHTB apparatus was performed in numerical simulation method, then corresponding incident tensile stress wave was studied and optimize improvement measures for partial components were also proposed. The partly improved SHTB apparatus reconciled the demands of glued connect mode, hooked connect mode and so on. At last, concrete was considered as a two-phase composite material which composed of coarse aggregates and cement matrix, the annulus three-dimensional concrete aggregate model was established and applied to SHTB simulation experiment. The comparison between numerical simulation results and experimental results verified the effectiveness of partly improved SHTB apparatus, which also provided research directions for dynamic tensile responses of mesoscopic concrete model.