PSI - Issue 28

A. Saoud et al. / Procedia Structural Integrity 28 (2020) 491–501 Amal Saoud/ Structural Integrity Procedia 00 (2019) 000–000

500 10

of the same nature a large number of times for each notch, by asserting each time that the parameter to be estimated is in this interval, we would be wrong on average 15 times out of a hundred. According to previous studies like Hiroshi Yushihara, MAL de silva in the ZEPR in which the material gradually softens, the notched specimen often behaves as if the slit is longer than its current length. The low rigidity in the ZEPR generally induces an increase in the compliance of the loading. This can clearly explain why the 4ENF specimen presents a significant instability during the propagation of the crack compared to the specimen already studied in the first part. In fact, the fracture surface for this specimen is more extensive and the risk of bifurcation is then higher.

Fig .10. Evolution of the stress intensity factor K IIC as a function of the length of the notch

5. Comparison between the results of the 4ENF test and those of the designed specimen In this part we are interested in comparing the results obtained from the test on the designed specimens with those of the 4ENF test considered the most reliable among the others but which also presents data acquisition difficulties. Figures 11 and 12 respectively present a comparison between the energy release rate and the stress intensity factor obtained from the test on the study specimen as well as those of the 4ENF test for the Eucalyptus Grandis.

0 100 200 300 400 500 600 700 800

The energy release rate (N/m)

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

(a/W)

Fig .11. Comparison between the energy release rate of the test studied and the 4ENF test