PSI - Issue 19

Okan Yılmaz et al. / Procedia Structural Integrity 19 (2019) 302 – 311 Yılmaz et al. / Structural Integrity Procedia 00 (2019) 000–000

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Fig. 5. Finite-element simulation results of the plate (bottom view - tensile side). Dashed lines illustrate the projection of the bolt head and flange diameters. Contact status shows the slip region where fretting failure might occur: (a) slip map when the top roller displacement is maximum, (b) slip map when the top roller displacement is minimum (found by multiplying the maximum displacement by the load ratio, R = 0 . 1). (c) Smith Watson-Topper (SWT) parameter providing the expected failure location, which is confirmed by the experiments (d). Fretting marks are observed under the flange.

5. Results and discussion

We analyzed the fatigue response of HSS bolted connections under in-plane shear and out-of-plane bending loading modes using experimental and numerical approaches. The experiments were designed to highlight the e ff ects relevant to the fatigue performance of bolted assemblies. Figure 6 summarizes the fatigue life improvement achieved in the considered materials taking punching with flat punch as the base level. We found that the chamfered punch was an improvement only when it was aligned to the loading direction as the sharp edge does not face the expected failure location. In [23], similar results can be found for punched specimens. While significant improvements were achieved via water-jet cutting technique, laser cutting was the best one, giving run-outs (5e6 cycles) in all cases. The performance of laser-cut specimens were much better compared to the ones reported in [24] while plasma-cutting performance were similar. For the complete fracture analysis of the hole-making processes, see [11, 12]. In general, fatigue results did not indicate an increased fatigue performance with increase bolt pre-tension under in plane shear loading. The e ff ect of the pre-tension on the fatigue performance of the connection was slightly di ff erent for each grade. Bolted connections in S500MC with a lower pre-tension performed better at lower stress amplitudes, while no significant di ff erences were observed at medium and higher load levels between bolt pre-tension classes. Fatigue performance of bolted connections made of S700MC was similar without any substantial e ff ect of the pre tension. The fatigue results however had a larger spread, mainly caused by some of the samples failing in a mixed