PSI- Issue 9

Khadija Kimakh et al. / Procedia Structural Integrity 9 (2018) 243–249 Khadija.KIMAKH / Structural Integrity Procedia 00 (2018) 000–000

247

5

0.15 mm/rev to f 3 = 0.05 mm/rev the number of cycles to faillure increase clearly with a percentage of 30% for σ max = 550MPa and 184% for σ max = 500MPa (figure 4).

600

f = 0.25 mm/rev f = 0.15 mm/rev f = 0.05 mm/rev

550

500

450

400 σmax MPa

350

300

10000

100000

1000000

10000000

N f cycles

Fig. 3. S-N curves of machined AISI1045.

Fig. 4. Evolution rate of change of N f function of feed rate.

Youngsik Choi (2015) investigated the influence of feed rate on surface integrity and fatigue strength of machined surface. He showed that the feed rate significantly affects fatigue life. The crack initiation lifetime as well as the propagation lifetime decreased with the increase of feed rate. The S-N curves of the machined AISI 1045 prove that the fatigue behavior is influenced by the surface roughness which is conditioned by the cutting conditions (the feed rate in our case). In what follows, surface state observations of fatigue specimen will be examined to see the modifications generated on surface roughness by the feed rate which affect the fatigue lifetime. 3.2. Effect of feed rate on surface state. Figure 5 shows global observations of the generatrix for fatigues specimens taken by optical microscopy.