Local strains and mesoscopic mechanisms of crack growth in 25Kh1M1F steel

Fatigue crack growth characterization requires non-homogeneous strain field measurements, the use of specific tech- niques is necessary. In this paper, the efficiency of the automated grid method for measuring in-plane displacements in the presence of high strain gradient is discussed. Vectors fields of displacement and strain gradient near crack tip have been stud- ied: macrostrain localization, mesostrain concentration at a crack tip in a 25Kh1M1F steel, and micromechanisms of fracture on a crack front.