Issue34

Z. Marciniak et alii, Frattura ed Integrità Strutturale, 34 (2015) 1-10; DOI: 10.3221/IGF-ESIS.34.01 8 angle  = 60  , where decrease in these values was confirmed. Considerable increase of parameter  J I and  J III values was observed with rising fatigue crack growth rate (Fig. 5, curves 1 to 2). Diagrams 1 and 2 shown in Fig. 5 concern fatigue crack growth rates: da/dN = 1.68  10 -8 m/cycle and da/dN = 4.23  10 -8 m/cycle, respectively. Figure 4 : Energy fatigue characteristic for steel C45. Figure 5 : Comparison of experimental results for different bending to torsion ratios with those calculated according to the Eq. (18) for 18G2A steel [27]. Different bending (cracking mode I) to torsion (cracking mode III) ratio in AlCuMg1 alloy is shown in Fig. 6. Fig. 6 [28] provides grounds to observe shift of experimental points towards increasing the values of parameter  J I - these increment values were lower than for steel 18G2A. Experimental results of interdependences between cracking mode I and III, for constant da/dN ratio value were defined by Eq. (18). Diagrams 1 and 2 shown in Fig. 6 concern fatigue crack growth rates: da/dN = 7.64  10 -8 m/cycle and da/dN = 1.41  10 -7 m/cycle, respectively.