PSI - Issue 18

Ibrahim Al Zamzami et al. / Procedia Structural Integrity 18 (2019) 255–261 Author name / Structural Integrity Procedia 00 (2019) 000–000

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Table 2. Summary of the statistical re-analyses for the different welded geometries.

series

No. of Data

R

t (mm)

a (mm)

Z (mm)

k

T σ

Δσ A,50% (MPA)

Δσ A,97.7% (MPA)

Butt-joint

12 15 10 12 10 10 11 12

-1

1.97

1.96 1.92

- -

7.5 3.4 7.0 2.8 6.8 1.7 9.0 3.4 6.3 2.1 5.8 1.3 2.9 2.3 5.9 1.5

20.1 31.9 38.4 36.2 36.2 25.5

10.9 19.3 29.3 19.5 24.9 21.7 87.9

0.1 1.02

Cruciform-joint

-1

1.98

- - - - - -

3.66 5.25 2.72 4.94 5.61 5.56

0.1 1.02 0.1 1.01 0.5 1.97

Lap-joint

Tee-joint

-1

1.96

132.4 175.6

0.1 1.94

145.7

The results of the reanalysis generated, in terms of the nominal stress approach, by post-processing the experimental data according to the statistical procedure reviewed in (Susmel 2009) are summarized in Table 2. The endurance fatigue limit ranges presented in Table 2 are extrapolated at 2 ∙ 10 6 cycles to failure for a probability of survival, P s equal to 50% and 97.7%. The same results are presented in Figure 3, in log-log Wöhler diagrams for the different welded configurations being investigated along with the recommended design curves (i.e. the IIW, EC3 and EC9) to allows the direct comparison of the experimental results with the standard design curves.

(a)

(b)

(c)

(d)

Fig. 3. Accuracy of the nominal stress approach to estimate the fatigue strength of the thin hybrid welded joints.

Table 2 and the Wöhler diagrams of Figs. 3a-c clearly show that a much higher negative inverse slope, k, was determined for each welded configuration being investigated compared to the values of 3 and 3.4 recommended by