PSI - Issue 5

D. Rozumek et al. / Procedia Structural Integrity 5 (2017) 896–903 D. Rozumek et al. / Structural Integrity Procedia 00 (2017) 000 – 000

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900

a)

b)

c)

Fig. 4. CTS (load angle θ = 45°) specimen in the last stage of fatigue crack growth: a) real crack paths, b) discrete model with predicted crack path, c) Huber-Mises stress distribution during the rupture.

Fig. 5 presents results of fatigue crack growth versus the number of cycles for mixed mode I+II and mixed mode I+III. For mixed mode I+III, the active side was considered because stresses by active side are bigger than by passive side. Therefore, these stresses have the main impact on failure of the specimens. a) b)

Fig. 5. Fatigue crack growth versus number of cycles under mixed mode: a) I+II, b) I+III.

From the graphs in Fig. 5a it appears that changes of the angle  from 30 o to 45 o are accompanied by increase of fatigue life of the specimens for mixed mode I+II and load ratio R = 0.1. However, when changing the angle  from 30 o to 45 o for mixed mode I+III (R = 0), the reverse situation is observed. The test results for the fatigue crack growth rate versus the stress intensity factor range, shown in Figs. 6-8, have been obtained from the Huber-Mises criterion for proportional loading

K K K , II I eq 2 2 3     

(1)

K K K . III I eq 2 2 3     

(2)

For CTS specimen the closed form solutions of SIFs presented by Richard (1985)