PSI - Issue 5

Valeriy Lepov et al. / Procedia Structural Integrity 5 (2017) 777–784 Valeriy Lepov et al. / Structural Integrity Procedia 00 (2017) 000 – 000

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Rp 0.2. An interval between these two values serve us as maximum starting point for the fatigue loading for each specimen. This cyclic loading was constant on the specimens under a constant frequency of 5 Hz until fracture and complete rupture occurs on the specimen (see Fig.3).

Table 4. Corrected tensile test result. No S 0 , [mm] L 0 , [mm]  p 0.2 , [ МPа]

 b , [ МPа]

 , %

1 2 3 4 5 6 7 8 9

84.08 85.67 73.92 84.16 80.67 83.21 85.91 83.37

52.00 52.00 52.00 52.00 52.00 52.00 52.00 52.00

328.35 484.50 22.18 322.08 477.24 20.95 314.62 488.12 23.55 335.97 482.68 21.72 335.90 485.46 25.93 323.45 484.79 21.83 318.22 479.69 20.91 340.22 485.18 23.20

removed

 , MPa

N, cycles

Fig. 3. S-N curve for a low cycle tested fatigue tested specimens.

Amongst the ten specimens used for the test, nine of the specimens were broken not at the welded portion but on the base metal. This can only interpret a good weld done with little or no defect. However one of the sample was broken on the welded portion before reaching its elastic limit, this signified a defect that could be due to WPS (Welding Procedure Specification), hydrogen inclusion, amongst others. A further research on the microstructure will give more light to the cause of this problem.

3. Modeling results and discussion

The modeling of damage accumulation processes should consider the complex effects of high-cycle fatigue and low-cycle impact loading and also friction damage. The impact toughness as shown in Table 3 greatly depends on the test temperature. So the overall damage  could differentiate for high-cycle fatigue damage  F and low-cycle impact damage  L and contact wear damage  Fr :