PSI - Issue 42

Lucie Malíková et al. / Procedia Structural Integrity 42 (2022) 1082–1089 Lucie Malíková et al. / Structural Integrity Procedia 00 (2022) 000–000

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equivalent, Rozumek et al. (2018) proposed, according to the Huber-Mises criterion for proportional loading, the following equivalent stress intensity factor range (ESIFR): ∆ eq = �∆ I � + 3∆ I � I . (1) For purposes of this paper, the value of the threshold stress intensity factor range was considered  K th = 9 MPa·m 1/2 . This value is assumed to be typical for high-strength steels with the yield strength of about 500 MPa, as can be found for instance in Wang et al. (2022). Of course, the analysis can be tailored to any other material and its fracture properties. 4. Results and their discussion As explained in the previous sections, the dependences of the ESIFR on the crack length were investigated for various configurations:  different values of the initial crack inclination angle  = -45, -30, -15, 0, 15, 30 and 45°;  different length of the corrosion pit 2 P = 0.5, 2 and 4 mm. Thus, three plots can be presented – Fig. 3 for the smallest corrosion pit with 2 P = 0.5 mm, Fig. 4 for 2 P = 2 mm and Fig. 5 for the largest corrosion pit with 2 P = 4 mm. The values were calculated for the selected range of the crack lengths as introduced in the previous sections (from 0.1 to 4 mm). The complete set of data is always plotted on the left, whereas a special attention is devoted to the part of the plots corresponding to shorter crack that are more affected by the presence of the corrosion pit. Therefore, this part of the results is displayed in detail on the right side of Figs. 3 to 5.

(a) (b) Fig. 3. Equivalent stress intensity factor range as a function of the relative crack length for various crack inclination angles (-45° to +45°) and corrosion pit of the length 2 P = 0.5 mm: (a) whole crack range investigated (between 0.1 and 4 mm), (b) short cracks (between 0.1 and 1 mm). The results presented via plots in Figs. 3 to 5 can be discussed with respect to individual parameters. The resulting statements are divided into several sections.

4.1. Dependence of the fatigue parameter  K eq on the crack length

Regarding the effect of the crack length on the ESIFR, a very simple conclusion can be summarized: with increasing crack length, the values of the  K eq increase as well. Furthermore, the dependences obtained are influenced by both other parameters (  and 2 P ), see the following discussion.