Influence of end friction confinement on dynamic mechanical properties and damage evolution of concrete by coupled DEM-FDM method

Abstract

This paper presents a quantitative evaluation of the effect of end friction on the dynamic mechanical response and damage evolution of concrete based on the coupled Discrete Element Method (DEM) - Finite Difference Method (FDM) method. Considering the heterogeneity of concrete, a three-phase meso-scale model of concrete (mortar, aggregate and interfacial transition zone) is constructed by DEM, and the crushability, real geometry and random distribution of aggregates are considered by combining 3D scanning techniques and the “ball-clump-cluster” method. Meanwhile, the split Hopkinson pressure bar (SHPB) device is constructed by FDM, and the interface deformation coordination between the concrete sample and metal rods is realized by coupling algorithm. On this basis, the quantitative effects of end friction on the stress–strain response, dynamic increase factor (DIF), damage distribution and failure mode of concrete are investigated. The results indicate that the dynamic compressive strength increases significantly when the interfacial friction coefficient μi increases from 0 to 0.1, and the interfacial friction enhancement effect weakens significantly when >0 μi.1. With the increase of strain rate, the friction contribution coefficient tends to decrease. The end friction has a significant effect on the distribution of microcracks in the axial direction. The end friction confinement changes the local stress state and damage distribution of concrete, which is beneficial to improve the compressive strength of concrete.