PSI - Issue 13

Fidan Smaili et al. / Procedia Structural Integrity 13 (2018) 1347–1352 Fidan Smaili, Tomaž Vuherer / Structural Integrity Procedia 00 ( 2018) 000 – 000

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b Fig. 2 (a) Geometry of the Charpy specimen; (b) Geometry of the fatigue crack growth specimen

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b Fig. 3. (a) The RUMUL Crakctronic and Fractomat machine; (b) Clamping of the fatigue crack growth specimen

3. Results

Microstructure examinations were carried out on light microscope Nikkon Ephihot 300. The artificially made CG HAZ and artificially FG HAZ microstructures were analyzed at different magnifications from 100  to 1000  . The CG HAZ microstructure is presented in Figure 4a and the CG HAZ microstructure is shown in figure 4b. In both cases the microstructure mainly consists of the laths martensite. The average size of CG HAZ crystal grains is approximately 200 µm and the average size of CG HAZ crystal grains is approximately 10 µm. Results of tensile test and hardness measurements are plotted in Table 2 and Table 3.

Fig. 4. (a) The CG HAZ microstructure; (b) The FG HAZ microstructure

Table 2. Results of the hardness measurements

Table 3. Results of the hardness measurements Microstructure Average Hardness / HV10 CG HAZ 458 FG HAZ 380

R p02 / MPa

R m / MPa

A 5 / %

Microstructure

CG HAZ FG HAZ

1042 1185

1431 1475

11,4 1475

Force versus time and energy versus time diagrams were recorded during Charpy instrumented tests. Total energy has been split into energy for initiation and energy for propagation. F - t and E - t diagram are shown in Figure 5 for the FG HAZ microstructure and the CG HAZ microstructure. And their split energy are presented in table 4.

Table 4. Results of the instrumented Charpy tests

A v = E t / J

E i / J 38.3 35.9

E p / J 20.3 22.2

Microstructure

KV / J/cm 2

Part of ductile fracture /%

CG HAZ FG HAZ

58.6 58.1

73.3 72.6

64 47