Issue 43

F. Majid et alii, Frattura ed Integrità Strutturale, 43 (2018) 79-89; DOI: 10.3221/IGF-ESIS.43.05

[12] Bathias, C., Pineau, A., Fatigue of Materials and Structures, (2013). DOI:10.1002/9781118616994. [13] Lemaitre, J., Desmorat, R., Engineering Damage Mechanics, (2005). DOI:10.1007/b138882. [14] Majid, F., Elghorba, M., HDPE pipes failure analysis and damage modeling, Eng. Fail. Anal. (2017). [15] Majid, F., Nattaj, J., Elghorba, M., Pressure vessels design methods using the codes, fracture mechanics and multiaxial fatigue, 38 (2016) 273–280. DOI:10.3221/IGF-ESIS.38.37. [16] Majid, F., Ouardi, A., Barakat, M., Elghorba, M., Prediction of PPR and HDPE polymers through newly developed nonlinear damage-reliability models, Procedia Struct. Integr., 3 (2017) 387–394. DOI:10.1016/j.prostr.2017.04.043.

N OMENCLATURE

Δe

Thickness fluctuation of each created notch (groove).

e n

Thickness of the pipe.

Instantaneous number of cycles under an applied stress.

Total number of cycles at the rupture.

N f

β

Life fraction representing the thickness fluctuation over the pipe’s thickness (β = Δe/e).

βc β Pa

Critical life fraction.

Life fraction corresponding to the pressure before rupture.

P

Burst or limit pressure.

Ultimate pressure corresponding to a neat HDPE specimen. Maximum pressure of the internal pressure curve of neat HDPE pipes

P u

P max

P r

Rupture pressure of HDPE pipes.

Ultimate residual burst pressure of notched pipes.

P ur Pa P ur1

Pressure just before the rupture corresponding to the last possible notch. , P ur2 , , Pa Ultimate residual burst pressure of notched pipes according to the notch level. α Parameter depending on the studied material (α = Pmax/Pr). η

Parameter depending on the applied pressure corresponding to the notch just before rupture (η =Pa/Pr).

D 0

, D i

External and internal diameters of a cylinder.

σ y

Yield stress. Ultimate stress

σ UTS P (β) D (β)

Continuum burst pressure as a function of the life fraction β, Continuum damage as a function of the life fraction β. Static damage based on burst pressures of HDPE pipes.

Ds

D

Linear damage of Miner.

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