Initiation and growth of corrosion-fatigue cracks near stress concentrators in V95pchT2 aluminum alloy

We investigate the kinetics of small fatigue cracks starting from notches in samples of V95pchT2 aluminum alloy in air and in a 3.5% NaCl solution. The influence of salt water is manifested in the initiation of pits on the notch surface and subsequent accelerated growth of small cracks (2-3 times faster than in the laboratory air). The size of an initial macrocrack a(i) does not depend on the level of stress or strain, notch radius, or environment and is equal to the characteristic distance d* = 100 mu m of the pre-failure zone which is a material constant. The effect of crack closure in the presence of a corrosive medium is observed at the crack length a > 100 mu m. Within the frameworks of the approach proposed earlier for the study of initiation of a macrocrack near a notch, the basic dependences of values of local stresses or strains on the duration of the period of initiation of a macrocrack with length a(i) = d* are established, and the standard diagrams of cyclic crack resistance are constructed for V95pchT2 aluminum alloy at the stage of macrocrack growth in air and in a 3.5% NaCl solution.