Modeling of Fatigue Crack Growth Kinetics Under Biharmonic Loading

The study is devoted to the investigating of the influence of biharmonic cyclic loading on fatigue crack growth kinetics. This type of loading - cyclic low-frequency loading with high-frequency harmonic oscillations superimposed on it - is characteristic of many real structures. In the study, steel flat compact specimens subjected to eccentric tension were used. The influence of high-frequency component of cyclic loading on fatigue crack growth was evaluated at different values of loading parameters: asymmetry, amplitude, frequency ratio of basic and harmonic loading. In work an algorithm for taking into account influence of sequences of superimposed high-frequency loading cycles on low-frequency component of loading based on consideration of stresses change near the mouth of developing crack and its influence on change of threshold value of stress intensity coefficient in this point has been applied. A comparative analysis of the crack growth duration by the “cycle-by-cycle” calculation and the experimental data obtained has been carried out.