Three-point bend test analysis using digital image correlation: from elasticity to damage

Abstract

Three-point bend tests give access to analytical solutions for identifying mechanical parameters of constitutive models, making it a widely used method for analyzing the behavior of cementitious materials. However, a lack of knowledge regarding the kinematics, such as the Dirichlet boundary conditions, may bias the parameter identification. This paper proposes a methodology to analyze the kinematics of a three-point bend test, from elasticity to damage, and to explicitly compute the mechanical parameters without any kinematic assumptions. The kinematic fields are measured using Global Digital Image Correlation, employing a kinematic basis derived from Timoshenko–Ehrenfest beam theory for the elastic stage, and T3 shape functions for the post-peak stage. Using such bases allows for the direct calculation of the Young’s modulus, tensile strength, and fracture energy. The identified material parameters are close to those obtained through Finite Element Model Updating (FEMU) using a simple elastodamage model.