Variations in fracture energy of concrete subjected to cyclic freezing and thawing
Abstract Fracture energy is one of the fundamental parameters representing cracking resistance and fracture toughness of concrete. The paper deals with the effect of internal frost damage on the fracture energy of concrete. The fracture energy value was assessed on beams with initial notches in three-point bend test assuring stable failure of the specimen. It was found, that the internal damages due to cyclic freezing and thawing have a significant effect on variations in fracture energy, related to changes in destructive load value as well as in deformability of material. The analysis of load-deflection curves obtained made it possible to fit the simple function, describing the post-peak behaviour of concrete subjected to frost damages, which can be useful for the calculation of G F value. It was proved that it is reasonable and feasible to study the freeze-thaw damage process of concrete using fracture mechanics methods.
HT5SS]In this paper, first, the basic theories of calculating stress intensity factor at a crack\|tip by FEM are provided. Then, the stress intensity factors are calculated about thick\|walled cylinders with various crack size internal semi\|elliptical surface crack under autofrettage residual stresses and its change laws are studied. These researches in this paper are very valuable to design, making and fatigue analysis about thick\|walled cylinder structure.