Determination of the threshold for the development of fatigue cracks in steels used in railway structures

Results of experimental studies of the cyclic resistance to cracks of 20GFL steel used in cast truck bolsters of freight cars are presented. Experiments were conducted for two values of the loading cycle asymmetry factor. Regularities in the growth of cracks near the threshold of their development are analyzed. The conditional threshold level of the stress intensity factor is determined for the studied steel. Different methods for determining this factor are considered.