Study on fracture behaviors of concrete using electronic speckle pattern interferometry and finite element method

Abstract

In this study, Electronic Speckle Pattern Interferometry (ESPI) technique was used to measure the surface displacement and strain fields around cracks in concrete beams. ESPI has high accuracy and can determine full-field deformations of concrete. However, tiny rigid-body movements of beam specimens can spoil the ESPI measurement and cause virtual deformations and false strains. Based on the theory of geometrical optics, this paper proposes a method to eliminate the false strains caused by rigid-body motion. The correction procedure was validated experimentally. Furthermore, the crack evolution in a pre-notched beam is presented. The critical minimum crack width of a microcrack is found to be about 0.1µm and the minimum crack width of an open crack is about 2 µm. Finally, a finite element analysis of a notched beam was conducted. The numerical and experimental results reveal that the critical crack tip opening of a notched beam is around 30-35 µm.