The 3D meso-scale model and numerical tests of split Hopkinson pressure bar of concrete specimen

In the present study, a 3D meso-scale model of plain concrete has been developed with consideration of the aggregates, mortar and interface transition zone (ITZ) between them. Firstly, the generation methods of the random polyhedron aggregate and ITZ are introduced, as well as the process how to create the meso-scale finite element (FE) model of the concrete specimen through grid mapping method. Then, based on the experiment data and repeated numerical simulations, the appropriate material parameters of HJC model with respect to each ingredient in concrete are determined. Based on the waveform data and the specimen deformation and failure process in the split Hopkinson pressure bar (SHPB) test of the concrete specimen, the validation of the numerical model is well verified. Subsequently, the numerical SHPB tests of concrete specimen with the experiment size of Phi 120 x 100 mm under various strain rates are performed. The formation processes of four typical failure patterns of the concrete specimen in the experiment are well reproduced, i.e. "slight-spalling", "breaking", "fragmentation" and "comminution". What's more, the cracking mechanism of concrete specimen in SHPB test is revealed. The formation mechanisms of various failure modes of the concrete specimen under different strain rates are further investigated. The research results show that the failure process of the concrete specimen in the SHPB test can be well simulated by the 3D meso-scale model developed in this paper. Furthermore, the accumulation of the tension strain damage in concrete is the main reason to initiate the cracks in the loading process. Under different loading conditions, due to the crush failure and the tension breaking failure derived from the compression expansion effect play different roles, the specimen deformation and failure processes of different modes will be exhibited. (C) 2017 Elsevier Ltd. All rights reserved.