13th International Conference on Fracture June 16–21, 2013, Beijing, China -4- Figure 4. Fretting scars and cracks of specimen no.9 and no.10 Figure 5. Comparison between fatigue S-N curve of the standard specimens and fretting fatigue S-N curve of the tube specimens Table 2. Length of the wear scars and distance from the crack to the middle of the fretting wear scar Specimen l1 d1 l2 d2 No. (mm) (mm) (mm) (mm) 6 2.3346 0.7933 2.4620 0.0726 7 2.6682 0.7525 2.3803 0.5883 8 2.4273 0.3545 2.3914 0.4456 9 2.4506 0.7165 2.5363 0.0740 10 2.5883 0.7197 2.5820 0.7666 11 2.5391 0.6570 2.4372 0.4760 12 2.7890 0.6986 2.5711 0.4131 13 2.2308 0.5218 2.3587 0.3494 14 2.2524 0.5993 2.1378 0.5708 15 2.3581 0.3850 2.2173 0.6122 3. FEM simulation 3.1 FEM model Because of the symmetry of the structure, a quarter model of pad-on-tube structure is employed as shown in Fig. 6. The size of the tube is Φ10mm×0.7mm×100mm. Symmetrical boundary condition is applied on plane XoZ and XoY. Clamped boundary condition is applied on plane YoZ. P is the applied contact pressure on the back of the pad. Dload is the displacement load on the top end of the tube. Fig. 7 shows that the applied contact pressure keeps 7.5MPa during the displacement load
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