PSI - Issue 3

Fatima Majid et al. / Procedia Structural Integrity 3 (2017) 387–394

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Fatima Majid et al. / Procedia Structural Integrity 3 (2017) 387 – 394

From the curve above, we notice that both of the mechanical behavior of the HDPE and PPR polymers have a ductile behavior. The curve trends can be interpreted through four phases. The first phase is a preloading stage, very short (2s) for PPR and longer (35 s) for HDPE. The second phase is the elastic stage, higher for HDPE and lower for PPR. Then, the plastic stage which very short for PPR and longer for HDPE. Finally, the last stage corresponding to rupture which very high for PPR and Lower for HDPE. Indeed, the limit pressures at the end of the elastic phase and the rupture one are behaving in a reverse way. Moreover, the time of burst of HDPE is very important than the PPR material which confirm that the first one stand the increasing pressure for long time. Another comparison is done between PPR and 15 years old HDPE. So, we notice that the old HDPE pipe has a similar behavior to the PPR one. Both of them have a tendency to a fragile behavior due to the reduction of the elastic limit, an increasing of the rupture one and the short time of the preloading (2s) and the plastic (3 s) stages.

Neat PPR Notched PPR 1mm Notched PPR 2mm Notched PPR 3mm Notched PPR 4mm Notched PPR 5mm Notched PPR 6mm Notched PPR 7mm Notched PPR 8mm Notched PPR 9mm Notched PPR 10mm

100 110 120 130 140

0 10 20 30 40 50 60 70 80 90

Pressure (bar)

0

2

4

6

8

10

12

14

16

18

Time (s)

Fig. 2. Internal pressure evolution for neat and notched PPR pipes.

70

Pressure of undamaged pipe Pressure for notch of 3 mm Pressure for notch of 4 mm Pressure for notch of 5 mm Pressure for notch of 1 mm Pressure for notch of 2 mm Pressure for notch of 1,5 mm Pressure for notch of 2.5 mm Pressure for notch of 3.5 mm Pressure for notch of 4.5 mm

60

50

20 Pressure (bar ) 30 40

10

0

25 Time (s)

0

5

10

15

20

30

35

40

45

50

Fig. 3. Internal pressure evolution for neat and notched HDPE pipes.