PSI - Issue 75

Fritz Wegener et al. / Procedia Structural Integrity 75 (2025) 363–374 Wegener et al. / Structural Integrity Procedia 00 (2025) 000–000

367

5

The test procedure is in alignment with the specifications of DIN 969 (2020-02). The tests on the bolting assemblies of nominal diameter M12 were carried out on a high-frequency pulsator from Z wick R oell at theU niversity of A pplied S ciences W ismar . For the tests on the nominal diameter M56 a 2 MN high-frequency pulsator from S incotec was used at the F raunhofer IGPR ostock , see Figure 3.

Fig. 3: (a) Test setup and bolting assemblies for test series M1-M12-b-sv and M2-M12-hdg-sv; (b) Test setup and bolting assemblies for test series M2-M56-b-sv / sg and M2-M56-hdg-sv.

In accordance wit EC3, at least four tests were carried out on three nominal stress levels resulting in at least n = 12 tests in the finite life of the S-N curve at a constant mean stress level of σ m = 0 . 7 · R p , 0 . 2 , nom = 630 N / mm 2 . The results of the experimental test series and the comparison with FprEN 1993-1-9 (2024-02) are summarized in Table 1. Table 1: Results of the statistical evaluation of fatigue tests on HV bolting assemblies of nominal diameter M12 and M56. Slope ∆ σ c , red , 95% Series 1) No. of data [-] [ N / mm 2 ] Detail category m var m const var. const. exp. FprEN 2) M1-M12-b-sv 13 3.21 65.4 65.3 63 56

M2-M12-hdg-sv M2-M56-b-sv M2-M56-b-sg M2-M56-hdg-sv

15 12 17 16

2.48 3.42 2.92 2.83

57.0 65.2

63

50

76.7 69.9 71 red 3) 81.3 85.6 90 red 3) 51.0 55.4 56 red 3)

56 red 4) 71 red 4) 50 red 5)

3

1) M1 - manufacturer 1 | M2 - manufacturer 2 | b - quenched and tempered black 1) hdg - hot-dip galvanized | sv - rolled before heat treatment | sg - rolled after heat treatment

2) acc. to FprEN 1993-1-9 (2024-02) 3) modified with reduction factor k 4) modified with reduction factor k 5) modified with reduction factor k

s acc. to Equation 1 and n = 0 . 10 acc. to Glienke et al. (2023)

s acc. to Equation 1 and n = 0 . 25 s acc. to Equation 1 and n = 0 . 10

It can be seen that the experimentally derived detail categories consistently exceed the values specified in the current draft of EC3. The positive e ff ect of the thread rolled after heat treatment is clearly evident when comparing the M2-M56-b-sv and M2-M56-b-sg series. The reduction in fatigue strength in the presence of hot-dip galvanization shows in the M2-M12-hdg-sv and M2-M56-hdg-sv series in the steeper variable slope of the S-N curve. A direct comparison with the non-galvanized state is only possible for the M2-M56-hdg-sv series. Here, the e ff ect of hot-dip galvanization is also reflected in a decrease of the test-assisted DC, which, however, is still above the value assumed according to FprEN 1993-1-9 (2024-02) taking into account the reduction factor k s .