PSI - Issue 41

Hendrik Baarssen et al. / Procedia Structural Integrity 41 (2022) 183–191

189

Baarsen et al. / Structural Integrity Procedia 00 (2022) 000–000

7

(a) Specimen B5

(b) Specimen B7

(c) Specimen B10

(d) Specimen B12

Fig. 4: Macroscopic appearance of the fracture surface for the pre-cracked specimens.

1,5

0,8 0,9 1 1,1 1,2 1,3 1,4

Reference tests Cracked specimen uncracked specimen

Reference Cracked specimen

1,0

average 1,15

N u,exp /N u [-]

N u ,exp /N u [-]

0,5

average cracked 0,97

0,0

B1 B2 B3 B4 B5 B6 B7 B8 B9 B10B11B12

0

0,5

1

1,5

2

el exp /el u,exp [kN]

Specimen

(a)

(b)

Fig. 5: (a) Normalized force elongation diagram of tensile tested specimens; (b) Comparison of test results

crack. Specimens that had no initiated cracks during the monotonic tensile test developed shear lips closer to the notch root. The obtained crack sizes varied from 1.0 mm to 7.0 mm. Figure 5a shows the load-elongation curve for all the tested specimens. The elongation is measured using a gauge length of 100mm, spanning over the hole. When comparing the normalized force-strain behaviour of specimen B7, B10, and B12 to the reference specimen B1 to B4, it shows di ff erent behaviour. The trend is similar up to about 0.8 N u , Rd . As expected, the pre-cracked notched plate specimens exhibit a lower ultimate load as compared to the reference notched plate specimens. Moreover, for the pre-cracked notched plate specimens the elongation measured at the ultimate load is lower as compared to the elongation measured for the reference notched plate specimens, and pre-cracked specimen show pop-ins indicating stable crack extension. Table 2 summarizes the results of specimen B5 to B12. In particular, the table reports the dimensions of the net section area, the amplitude of the applied force, the load ratio and the number of load cycles applied. Also, the failure load is predicted with Equation 3 and compared with the value measured during the experiments. In addition, the type and the depth of the cracks are reported. In Figure 5b the ratio between N u , exp and N u are plotted for all the specimens. Specimens B1 to B4 have an average ratio of 1.15. A similar ratio is achieved for specimens B9 and B11, which are partially fatigued, but have been tested up to failure prematurely, i.e. without a macro-crack being developed. Instead, specimens B5, B7, B10 and B12, which are partially fatigued and correctly pre-cracked, show an average ratio of 0.97, with a range [0.94-0.99].