PSI - Issue 28

Branislav Djordjevic et al. / Procedia Structural Integrity 28 (2020) 295–300 Branislav Djordjevic et al/ Structural Integrity Procedia 00 (2019) 000–000

297

3

displayed using a logarithmic coordinate system. The parameters of fitted Weibull distributions are then calculated analytically via “least square” method, i.e. using regression analysis in form given in [4, 13]. Scale parameter of Weibull distribution is expressed as J value when P ( J ) is 0.632 [14]. Both parameters were calculated and derived from experiments.



J        

(1)

  1

c P J

e

 

i

i P



(2)

1

N



1

1       2 B B



(3)

J J 

B

B

2

1

Table 3. J c values for CT50 specimens tested at -60°C. Specimen no. J c [N/mm] B [mm]

Displ.rate v [mm/min]

B net [mm]

EP1 EP2 EP 3 EP4 EP5 EP6 EP7 EP8 EP9 EP10 EP11 EP12 EP13 EP14 EP15 EP16 EP17 EP18 EP19 EP20 EP21 EP22 EP23 EP24 EP25

60.0

25.0 25.0 25.0 25.0 20.0 25.0 20.0 25.0 20.0 25.0 20.0 25.0 25.0 20.0 20.0 20.0 25.0 20.0 25.0 20.0 25.0 25.0 20.0 25.0 20.0

0.500 0.500 0.500 0.500 0.500 0.500 0.020 0.500 0.020 0.500 0.020 0.500 0.500 0.500 0.020 0.020 0.020 0.500 0.500 0.020 0.500 0.500 0.020 0.500

120.0 124.0 168.0 178.2 195.0 211.8 215.0 241.2 286.0 286.9 304.0 340.3 340.3 409.0 424.1 434.0 447.5 448.0 483.4 518.0 560.0 582.3 630.0 660.8

15.827

15.754

15.822

15.820

15.704 15.829 15.800

15.737

15.813

15.714

15.829

0.004 &0.50

3. Experimental results Notched CT50 specimens with two different thickness values were tested in accordance with relevant standards, and were made with side grooves equal to 20% of specimen thickness. Testing and determining of J c was performed in accordance with [10]. A total of fourteen CT50 specimens with following dimensions were tested: width, B = 25 mm (B net = 20 mm, side grooves on both sides were 2.5 mm). The second type of tested CT50 specimens had a width of B = 20 mm, wherein B net was 16 mm, and side grooves were 2 mm deep. A total of eleven such specimens were tested. Thus, a total of 25 specimens with two different thickness values were considered. Tests were performed on a commercial test machine, with a capacity of 20 tons. Displacements rates during testing of CT50 during testing were 0.5 and 0.02 mm/min. Cooling was performed in a chamber filled with liquid nitrogen, whereas temperature regulation