Investigations on influence of the plastic zone after single-peak overload on fatigue life of structural steel under tension

The authors proposed a new model of fatigue crack growth in 10HNAP structural steel. The model has been formulated on the basis of analysis of the known models and the experimental data obtained under cyclic tension with single-peak overload. The model proposed includes retardation of the fatigue crack growth, it describes the experimental results very well and allows to determine the structure life. The authors have shown that for low overloads the specimen life N-c reaches its minimum as the stress ratio R increases. For the higher overloads the specimen life N-c monotonically increases as R rises. The effect is connected with formation of a large plastic zone in the crack tip, formation of internal stresses and the slot closing.