PSI - Issue 25

Fatima Majid et al. / Procedia Structural Integrity 25 (2020) 430–437 Author name / Structural Integrity Procedia 00 (2019) 000–000

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curve. It shows that we reach the end of the stage I at a minimum value corresponding to βc1 equal to 21.5%. Meanwhile, the stage II of the damage ends at value of 75% giving rise for the damage acceleration until we get the ultimate one. Besides, the superposition of the curves of the model based on strains, as shown in Figure 3, gives an intersection at the life fraction βc3 of 85%. This life fraction is located in the third stage of the damage evolution. It has been proved in our work (Majid and Elghorba, 2016) that 52% is the critical life fraction for the neat HDPE pipes. Thus, we can say that this value is also the critical life fraction for the old HDPE pipes.

Fig. 2. Static damage evolution and reliability for an old HDPE Pipe based on energy.

Fig. 3. Damage and reliability evolution for an old HDPE Pipe based on strains.