PSI - Issue 37

Junpeng Li et al. / Procedia Structural Integrity 37 (2022) 582–589 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 7. Cracks initiation of the specimen observed by metallurgical microscopy.

3.2. Surface micro morphology analysis Select specimens with load cycle times of 5×10 4 and 1.6×10 5 respectively, and observe the contact surface by electron microscope (SEM), as shown in Fig.8.

(a) 5×10 4

(b) 1.6×10 5

Fig.8. Specimens surface observation by SEM

SEM observation shows that the pearlite is extruded and deformed under rolling contact load on the contact surface of the specimen, and micro-pores are formed after dislocation slippage. In the micro-pores, due to stress concentration, micro-cracks are initiated. Many micro-cracks have a tendency to be connected with each other, and finally join into sheets to form surface crack initiation. There are many states such as micro-pores and micro-cracks on the contact surface at the same time. Under different load cycle times, the proportion of each state is different, and the contact surface is always in a dynamic equilibrium process. 4. Conclusions The accuracy of the prediction method for the coexistence of rail surface fatigue crack initiation and wear is verified by using the method of the twin-roller fatigue test. The comparison is made from the aspects of wear, crack length and crack initiation position. And the specimens surface microscopic morphology observation and analysis by electron