PSI - Issue 23

Petra Ohnišťová et al. / Procedia Structural Integrity 23 (2019) 469 –474 Petra Ohnišťová et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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The crack propagations from the secondary phases to the material matrix at the angle of 45° (in the direction of the maximum shear stresses) before reaching the tensile strength limit (484 MPa) have been found – Fig. 6.

Fig. 5. DIC analysis of engineering strain in the intermetallic particle during tensile loading – before testing, at yield strength and at the tensile strength limit.

3.2. In-situ cyclic loading of 7475-T7351

The basic aim of the in-situ cyclic loading was to observe crack nucleation and propagation during the uni-axial cyclic loading. A matrix of twenty secondary phases in the functionally area of the specimen was observed during cyclic loading in parallel. The parameters of the cyclic fatigue loading were following:  the stress control: 35 MPa – 350 MPa (~ 245 N - 2,450 N), R=0.1  the speed: 100 N/s  imaging sequence at number of cycles: N=100, N=500, N=1,000, N=3,000, N=6,000.

Fig. 6. The cyclic fatigue loading: a) DIC study of engineering strain in the intermetallic particle during cyclic loading – at number of cycle N=3,000; b) hysteresis loops.