Issue 46

I. Čamagić et alii, Frattura ed Integrità Strutturale, 46 (2018) 371-382; DOI: 10.3221/IGF-ESIS.46.34 377 and by introducing the values of conventional yield stress, R p0,2 =  , [1, 17], the approximate values for critical crack length, a c , can be calculated. 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 PM-1-1n 20 60.1 117.8 38.5 PM-1-2n 63.9 121.4 40.8 PM-1-3n 58.6 116.3 37.5 PM-2-1n 540 43.2 87.2 40.0 PM-2-2n 44.7 88.7 41.4 PM-2-3n 45.3 89.2 41.9 Table 8: Values of K Ic notched specimens in new PM. 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 PM-1-1e 20 47.8 105.0 41.7 PM-1-2e 42.1 98.6 36.8 PM-1-3e 40.7 96.9 35.6 PM-2-1e 540 24.5 65.6 30.8 PM-2-2e 22.7 63.2 28.6 PM-2-3e 21.8 61.9 27.4 Table 9 : Values of K Ic notched specimens in exploited PM. The characteristic diagrams F-  , and J-  a for specimen taken out from the sample of new PM are given in Fig. 6 (left) for specimen marked as PM-1-1n tested at room temperature, and in Fig. 7 for specimen marked as PM-2-1n tested at the temperature of 540  C, [1]. 0 1 2 3 4 5 6 7 8 0 4 8 12 16 PM-1-1n 20 o C F, kN  , mm 0 1 2 3 4 5 6 7 8 0 50 100 150 200 250 PM-1-1n 20 o C J Ic = 60,1 kJ/m 2 J Ic J, kJ/m 2  a, mm Figure 6 : F- δ (left) and J- Δ a (right) diagrams of specimen PM-1-1n.