·Table of Contents ·Late Received Papers | ON THE NEW METHOD TO COMPUTE THE FATIGUE THRESHOLD - INFLUENCE OF THE MICROSTRUCTURE AND RESIDUAL STRESSESK.NECIB ; M.A. Belouchrani ; A. BRITAHLaboratoire Génie des Matériaux, Ecole Polytechnique Bp 17, Bordj-El-Bahri - Algérie, Tél. : (2132) 86.34.69 / (2132) 42.67.53 Fax : (2132) 86.32.04 Contact |
K_{I} < K _{S} no propagation | (1) |
K_{S} = a_{1}+b_{1} x^{1/2}, | (2) |
a_{lim} < a_{c} | (6) |
(7) |
Fig1: Modified notch and crack |
r_{f} = r + n e | (8) |
r_{f} = n e | (9) |
e » 5 x | (10) |
(16) |
Fig 2: Plate with lateral crack. | Fig 3: Independence of K_{SD} with a/W |
Material | designation | diameter of grain in | s_{s}en MPa | s_{u}en MPa |
Docol 350 | A | 8 | 260 | 360 |
SS 14147 | B | 15 | 185 | 322 |
HP steel | C | 29 | 210 | 304 |
HP steel | D | 45 | 160 | 279 |
HP steel | E | 82 | 120 | 242 |
Table 1: Diameter of the grain and mechanical material data. |
Designation | K_{S} | K_{sh} | K_{SD} |
A | 5.4 | 8.9 | 8.43 |
B | 6.0 | 7.6 | 6.49 |
C | 6.2 | 9.5 | 8.22 |
D | 6.7 | 8.1 | 6.8 |
E | 8.2 | 7.8 | 5.73 |
Table 2: Fatigue threshold and shakedown stress intensity factor |
Influence of the microstructure on the values of K_{SD}
For the materials given in Table 1, we show in figure (4) the influence of the grain size on the obtained shakedown stress intensity factor K_{SD} (Table 2) normalized by the corresponding yield stress, the results show that the ration fluctuates linearly with :
(17) |
(18) |
Fig 4: Relationship between |
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