Issue 46

I. Čamagić et alii, Frattura ed Integrità Strutturale, 46 (2018) 371-382; DOI: 10.3221/IGF-ESIS.46.34

16

250

PM-2-1n 540 o C

PM-2-1n 540 o C J Ic = 43,2 kJ/m 2

200

12

150

8

100 J, kJ/m 2

F, kN

4

50

J

Ic

0

0

0

1

2

3

4

5

6

7

8

0

1

2

3

4

5

6

7

8

 , mm  a, mm Figure 7 : F- δ (left) and J- Δ a (right) diagrams of specimen PM-2-1n. The influence of testing temperature on the value of critical stress intensity factor, K Ic , for specimens taken from the new and exploited PM is graphically illustrated in Fig. 8 (left), and the impact of the testing temperature on the critical crack length, a c , is graphically illustrated in Fig. 8 (right), [1].

200

100

Parent metal - PM New PM Exploited PM

Parent metal - PM New PM Exploited PM

160

80

120 Ic , MPa m 1/2

c , mm

60

80

40

40

20

Critical crack length, a

Fracture toughness, K

0

0

0

100

200

300

400

500

600

0

100

200

300

400

500

600

Testing temperature, o C

Testing temperature, o C

depending on the testing temperature for the PM (left) and change in value of a c (right)

Figure 8 : Changes in value of K Ic

, and critical crack length, a c

Calculated values of critical stress intensity factor, K Ic

, are given in the Tab.10 for notched

specimens in WM, tested at room temperature of 20  C and working temperature of 540  C, [1].

Testing temperature,  C

Specimen mark WM-1-1 WM-1-2 WM-1-3 WM-2-1 WM-2-2 WM-2-3

Critical J-integral, J Ic , kJ/m 2

Critical stress intensity factor, K Ic , MPa m 1/2

Critical crack length, a c , mm

72.8 74.3 71.1 50.2 52.6 48.4

129.6 130.9 128.1

20.2 20.7 19.8 17.4 18.2 16.8

20

93.9 96.2 92.2

540

Table 10 : Values of, K Ic

notched specimens at WM.

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