PSI - Issue 28

Najat Zekriti et al. / Procedia Structural Integrity 28 (2020) 1745–1754 Najat Zekriti and al/ Structural Integrity Procedia 00 (2019) 000–000

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G E 

2(1 )   Therefore, the stress intensity factor for mode-I can be obtained from the displacement of the crack opening. Fig.8 By:   2 2 8(1 ) I E Um K r     (2) Miannay (1995) gives the empirical formula based on the linear elastic fracture mechanics for the stress intensity factor for SENT geometry: ( ) I a K a f w    (3) ( ) f a w is a correction factor depends on the geometry of the structure. In our case, this factor is expressed by: 2 3 4 ( ) 1,12 0, 231( ) 10, 55( ) 21, 72( ) 30,39( ) a a a a a f w w w w w      (4) From the stress-strain curves obtained by the tensile tests at different crosshead speeds, we determined the flow stress for each crosshead speed namely 35,6 MPa and 29,3 MPa respectively for the extruded ABS and printed one These stresses are used to plot the variation of FICs, as a function of crack length, using formula (1). Fig.9. groups the results obtained.

a w

Fig.9. SIFs in function of β with   In these figure we will look at the curve of stress intensity factor in correlation to life fraction. It can be seen that the propagation of the crack for both samples occurs in three stages. The first stage corresponds to the initiation of the crack where it is stable, and then it evolves in a progressive manner, which is shown in the second stage, while the last stage corresponds to the sudden propagation, which leads to the failure of the specimen.