PSI - Issue 28

C.D.S. Souto et al. / Procedia Structural Integrity 28 (2020) 139–145

143

Carlos D.S. Souto et al. / Structural Integrity Procedia 00 (2020) 000–000

5

3. Fatigue test data and discussion

The presented setup was used to test Z-rail profiles (191 / 61 / 30 / 3.5) made out of S355MC steel, with a span of 880 mm. Fatigue testing was done with a loading ratio of R = 0 . 1. Table 1 shows the obtained results for each specimen that were tested with both downward and upward loading scenarios. In this table, the stress ranges are relative to the maximum principal stress ranges calculated in a linear elastic finite element model, where these were extracted from the rail’s web-flange corner (where fatigue cracks appeared during testing). Figure 5 shows the obtained S-N curves for both loading scenarios. As shown in Figure 5, the proposed Eurocode 3 category 160 MPa curve for plain steel produces a very conservative fatigue life prediction for the Z-rail profiles. Both downward and upward loading scenarios show very similar results, despite the expected distinction due to tensile and compressive residual stresses in the crack’s initiation sites. Both experimental S-N curves present a slope of around 7-8, which is significantly higher than the base values of the Eurocode 3.

Loading scenario

Maximum load [kN]

Frequency [Hz]

Stress range [MPa]

Cycles

Comments

3 . 25 · 10 5 5 . 00 · 10 6 5 . 00 · 10 6 5 . 00 · 10 6 5 . 50 · 10 5 8 . 00 · 10 5 5 . 80 · 10 5 3 . 25 · 10 5 2 . 20 · 10 5 1 . 20 · 10 5 1 . 60 · 10 5 1 . 20 · 10 5 2 . 00 · 10 5 9 . 50 · 10 4 7 . 50 · 10 4 4 . 25 · 10 4 9 . 00 · 10 4 4 . 50 · 10 4 5 . 00 · 10 6 5 . 00 · 10 6 5 . 50 · 10 5 6 . 50 · 10 5 7 . 00 · 10 5 9 . 00 · 10 5 8 . 50 · 10 5 7 . 00 · 10 5 5 . 50 · 10 5 6 . 45 · 10 5 2 . 00 · 10 5 2 . 55 · 10 5 1 . 80 · 10 5 2 . 40 · 10 5 4 . 50 · 10 4 6 . 20 · 10 4 2 . 20 · 10 4 6 . 40 · 10 4

Downward (D)

5 5 5 5

3 3 3 3 3 3 3 3 3 3 3 3 3 3 2 2 2 2 2 2 3 3 3 3 3 3 3 3 2 2 2 2 1 1 1 1

416 416 416 416 458 458 520 520 520 520 624 624 624 624 750 750 750 750 399 399 441 441 441 441 544 544 544 544 646 646 646 646 747 747 747 747

outlier run-out run-out run-out

D D D D D D D D D D D D D D D D D U U U U U U U U U U U U U U U U U

5.5 5.5

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

6.25 6.25 6.25 6.25

7.5 7.5 7.5 7.5

9 9 9 9 9 9

Upward (U)

run-out run-out

10 10 10 10

12.5 12.5 12.5 12.5

15 15 15 15

17.5 17.5 17.5 17.5

Table 1: Loading fatigue results.