車輪及びレール鋼における混合モード負荷による疲労き裂成長

抄録

Fatigue crack growth under mixed mode loading is an important problem in railway fields. Therefore, a method was developed and prepared to observe the fatigue crack propagation under mixed loading of tensile and in-plane shear modes by an in-plane biaxial fatigue machine. In the experiments, sequential and overlapping mode I and mode II cycles were applied to the crack in the cruciform specimen made of wheel or rail steel. Growth rate laws for wheel and rail steel were obtained by means of least square regression analysis in terms of both the effective stress intensity factor ranges. The fracture surfaces near the crack tip region of tested specimens were observed by SEM and discussed to relate the superiority of pearlite structure over tempered martensite structure in detail.