Studies on the cyclic crack resistance of high-strength steels for assessing the service life of deep-sea equipment

The practice of the determination of cyclic crack resistance, i.e., the rate of fatigue crack growth depending on the range of the stress intensity factor, has existed for more than a decade. However, a number of problems related to the use of these data for the quantitative assessment of the service life for deep-sea equipment remain poorly understood. They are description of crack kinetics under alternating and mainly compressive loading cycles and taking into account the possible impact of differences in loading frequency for a sample and for a structure in corrosive media. The investigation of the impact of these factors is performed using a technique for monitoring the changes in the compliance of a sample, which allows one to register the loads of crack opening and complete closing and crack propagation at small temporal bases under testing with reduction of the frequency to 0.01 Hz.