Issue 46

I. Čamagić et alii, Frattura ed Integrità Strutturale, 46 (2018) 371-382; DOI: 10.3221/IGF-ESIS.46.34 378 0 1 2 3 4 5 6 7 8 0 4 8 12 16 PM-2-1n 540 o C F, kN  , mm 0 1 2 3 4 5 6 7 8 0 50 100 150 200 250 PM-2-1n 540 o C J Ic = 43,2 kJ/m 2 J Ic J, kJ/m 2  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]. 0 100 200 300 400 500 600 0 40 80 120 160 200 Parent metal - PM New PM Exploited PM Fracture toughness, K Ic , MPa m 1/2 Testing temperature, o C 0 100 200 300 400 500 600 0 20 40 60 80 100 Parent metal - PM New PM Exploited PM Critical crack length, a c , mm Testing temperature, o C Figure 8 : Changes in value of K Ic depending on the testing temperature for the PM (left) and change in value of a c (right) Calculated values of critical stress intensity factor, K Ic , and critical crack length, a c , 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]. Specimen mark Testing temperature,  C Critical J-integral, J Ic , kJ/m 2 Critical stress intensity factor, K Ic , MPa m 1/2 Critical crack length, a c , mm WM-1-1 20 72.8 129.6 20.2 WM-1-2 74.3 130.9 20.7 WM-1-3 71.1 128.1 19.8 WM-2-1 540 50.2 93.9 17.4 WM-2-2 52.6 96.2 18.2 WM-2-3 48.4 92.2 16.8 Table 10 : Values of, K Ic notched specimens at WM.