Fatigue crack growth and microstructural analysis of rail steel specimens under periodic overloads

The present paper aims to study the effects of periodic overloads on the fatigue crack growth and microstructure of railway rail specimens. Numerical analysis and experimental tests were exploited to examine the crack path in specimens. A three-dimensional nonlinear boundary element model was used to predict the crack path in specimens. The effect of several parameters on the fatigue life of the rail steel specimens were evaluated using numerical model and experimental tests. The numerical and experimental test results revealed that the fatigue life curve had an optimal overload ratio at which the fatigue life was maximized. The number of fixed cycles was kept fixed between the overloads, measuring the effect of the overload ratio on the fatigue crack growth. Also, the fractographic analysis showed that by increasing the stretching speed of the rail steel specimens, the amount of plastic deformation is reduced and the brittleness of the material is increased.