PSI - Issue 37

Zijah Burzić et al. / Procedia Structural Integrity 37 (2022) 269 – 273 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

271

3

2.3. Fatigue testing – S-N curves Two types of testing were performed to assess behaviour of welded joints under amplitude loading, both without and with cracks. In the first case, standard specimens for testing of S-N curves were used, Fig. 3. Result is shown in Fig. 4, indicating relatively high fatigue strength 217 MPa.

.

500

Fig. 3. Specimen used for fatigue testing Most Gazela

S f = 217 MPa

400

300

200

100 N a p o n, S, MPa

0

10 4

10 5

10 6

10 7

10 8

Broj ciklusa, N

Fig. 4. The S-N curve for the base metal, S f =217 MPa

2.4. Fatigue testing – Paris law coefficients Fatigue testing with cracked specimens was performed according to the standard ASTM E647 15e1, [14], by using 3PB Charpy specimens and Fractomat device to monitor crack length, Fig. 5. Results are shown in Tab. 2, indicating high values of crack growth rate for amplitude loading corresponding to Δ K=10, 20 and 30 MPa∙ √ m. Crack growth rate (da/dN) versus stress intensity factor range ( ΔK) is shown in Fig. 7, as a typical S shaped curve with linear section defining Paris law.

I const

+

 V

+

Fig. 5. Charpy specimen and device for monitpering crack length

Table 2. Fatigue crack growth parameters C and m, according to Paris law, in perpendicular direction