Multi-scale modeling of the concrete SHPB test based on DEM-FDM coupling method

Abstract

The split Hopkinson pressure bar (SHPB) test is the most commonly used method for testing the dynamic mechanical behavior of materials at high strain rates. In this paper, for the SHPB test of concrete, an efficient multi-scale mechanical calculation method based on coupling of discrete element method (DEM) and finite difference method (FDM) is proposed, and SHPB test system for analysis of the macroscopic and microscopic dynamic mechanical properties and damage evolution of concrete under impact loading is established by this coupling method. A three-phase mesoscopic scale model of concrete is constructed by DEM, and the crushability, real geometry-shape, and particle size distribution of aggregates are considered by combining 3D scanning technology and the “ball-clump-cluster” method. Meanwhile, FDM is adopted to simulate the SHPB model, and the “coupling wall” mechanism is applied to realize the signal transmission between the models. On this basis, the stress waves obtained by the direct monitoring method through numerical simulation are basically consistent with those obtained by the theoretical calculation method, which verifies the dynamic characteristics of the SHPB model. Finally, the different types of microcrack propagation are analyzed in the premise of examining the static and dynamic mechanical response of the concrete model. It was found that the distribution of mortar and aggregate microcracks on the outside of the concrete was significantly more than that on the inside due to transverse inertia force, and the superiority of the method in simulating the damage evolution behavior of concrete meso-structural is demonstrated.