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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a finite element (FE) model (See in Fig. 1) was established according to the twin-roller specimen for calculating the contact stress and strain by the two specimen in order to simulate the wear, fatigue damage and its accumulation based on Archard’s wear model [13] and the critical plane model [18] respectively. For improving the efficiency the local grid at the contact area of the specimen FE models was refined.

(a) Global FE model

(b) Local submodel mesh refinemen

Fig.1. Twin-roller specimen FE Model

The two rollers in the twin-roller fatigue test rig were a rail (upper specimen) and a wheel roller (lower specimen) respectively. The diameter of two rollers was 60 mm and the contact track width was 5 mm. The rail rollers were cut from the rail head, shown in Fig.2. The radius of the contact profile in upper specimen was 80 mm for reproduce the curve with the same radius in rail profile occurring RCF crack frequently in field observation. The normal force of rail roller was about 2600 N. The slip ratio between two rollers was 0.2%.

(a) Sampling positions and dimensions of wheel and rail rollers

(b) Schematic of the twin-Disk testing machine

Fig.2. The test apparatus

The operation cycles were 5×10 4 , 8×10 4 , 1.2×10 5 , 1.6×10 5 , 2×10 5 , 3×10 5 cycles respectively. During the rolling test, the specimens were cooled by fans. After the test, the surface macroscopic morphology of specimens under different cycles conditions was analyzed by a Leica optical microscope (OM, Leica, Wetzlar, Germany). The surface microstructure of specimens under different cycles conditions was analyzed by using Zeiss Supra 55 field-emission scanning electron microscope (SEM, Zeiss, Oberkochen, Germany). The surface hardness was measured by using a FM-700 hardness tester (Future-Tech, Kanagawa, Japan) with a load of 2.45 N and dwell time of 15 s. The chemical