基于DIC 方法研究混凝土劈裂的变形和破坏

Concrete is a typical quasi-brittle composite material with tension-compression asymmetry. When the tensile failure is studied by Brazilian splitting test, different loading methods have great impact on the deformation and failure characteristics of concrete. The quasi-static splitting tests of standard disk direct loading, arc loading and flattened disk loading are carried out. Based on the digital image correlation method, the full-field deformation and localized failure characteristics in the process of concrete tensile splitting are studied. The results are as follows. (1) For the direct loading of the standard disk, the stress concentration near the top and bottom of the specimen makes the damage concentration occur preferentially at the end of the specimen, and the high amplitude area in the tensile strain field expands rapidly from the loading end to the center; due to the improvement of stress concentration by the arc loading and flattened disk loading, the strain concentration firstly appears near the center of the specimen and continues to expand from the center to both ends until the crack penetrates the specimen. (2) Arc loading and flattened disk loading meet the central initiation hypothesis of Brazilian splitting experiment; the tensile strength of concrete specimen measured by the flattened disk is about 5 MPa, which is about 31.2% higher than the standard disk due to the greater friction at the loading position and greater central compression tension ratio. (3) Under the three loading methods, the DIC analysis results of the deformation at the center of the specimen are in good agreement with the measurement results of the strain gauge, which verifies the effectiveness of the full-field deformation of the concrete specimen obtained based on the DIC method.