PSI - Issue 19

Jennifer Hrabowski et al. / Procedia Structural Integrity 19 (2019) 259–266 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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The S960QL series for butt welded plates are subdivided into "Hand" for hand-welded specimens and "Auto" for automated welded specimens. This subdivision is carried out because the different types of production exert a considerable influence on the residual stress distribution and the resulting fatigue strength.

Table 1. Fatigue test program Test series

Wall thickness

Steel

No. of tests

50d-8-96Q-Hand

t = 8 mm

S960QL

7

50d-8-96Q-Auto

t = 8 mm

S960QL

9

50d-8-96M

t = 8 mm

S960M

15

Butt welded plates

50d-8-11Q

t = 8 mm

S1100QL

13

40-8-96Q

t = 8 mm

S960QL

20

40-8-96M

t = 8 mm

S960M

20

40-8-11Q

t = 8 mm

S1100QL

20

attachment

Transverse

The loads are selected high, so that most of the tests have numbers of cycles to failure N f < 50,000. This should clarify how far the S-N-curve can be extended linearly into the low cycle fatigue range. For better comparability with existing S-N-curves and for statistical verification, some tests are also carried out in the high cycle fatigue range.

3.3. Test Set-up

The fatigue tests are carried out force-controlled under constant tension load amplitude with a stress ratio of R = +0.1. Therefore, a Losenhausen servo-hydraulic testing machine with 1000 kN maximum test load and an Instron with 250 kN maximum test load are used. A resonance testing machine from Schenck is used for verification tests in the high cycle fatigue range. The installation of the samples is done on all three testing machines via hydraulic clamping jaws.

3.4. Butt welded plates

At high loads and using high quality steels, a high quality weld is required. Therefore, a V-seam with an opening angle of 45 ° is chosen within the investigations of butt welds. So, the butt welds are carried out with sealing run and grinded root as illustrated in Fig. 1.

1 2 3 4

Fig. 1. Butt weld with sealing run and grinded root The plate thickness is on both sides of the weld t = 8 mm. The weld is executed 4-ply.

Transverse butt welds welded from both sides and checked by nondestructive testing can be classified in detail category 80 in EN 1993-1-9 (2010), if the height of the weld convexity is not greater than 20% of the weld width, with smooth transition to the plate surface. If the height of the weld convexity is not greater than 10% of the weld width, than detail category 90 is valid. The classification according to IIW (Hobbacher 2016) is analogous to FAT 80 or 90, respectively.