PSI - Issue 3

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Fatima Majid et al. / Procedia Structural Integrity 3 (2017) 380–386 Fatima MAJID / Structural Integrity Procedia 3 (2017) 380 – 386

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Damage of HDPE notched pipe of 3 mm depth ( γ=1,19) Miner Damage of CPVC notched pipe of 3 mm depth ( γ=1,26)

Damage

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Fig. 5. Comparison of HDPE and CPVC pipe’s unified theory damage.

4. Discussion The present work is an occasion to discuss and compare the burst behavior of two well-known polymers extremely used in the industrial field and specifically in the water piping networks. In order to make the quality checks easier without going through costly dynamic test, we leaded a study to compare HDPE and CPVC characteristics through static burst tests. The nondimentional analysis of burst pressures allowed us to evaluate the harmfulness of the defects and more significantly the punctual one. Indeed, the nondimentional curves showed that the two materials have a comparable damage whate ver the range of the used pipes and the pipe’s diameter. To overcome the difficulties of dynamic testing, we modified the stress controlled unified theory to take into consideration a new parameter which is the burst pressure. The Obtained damage curves showed that beyond the critical life fraction (Thickness reduction more than 50%) the curves become instable and the damage is not any more representable. The two material have almost the same damage behavior toward the parameter of burst pressure. Thus, we noticed that the damage, compared to the linear one, becomes more and more non-linear proportionally to the thickness reduction. Finally, we proposed a modification of the Faupel formula for the calculation of the burst pressure. This pressure can be used as a parameter in the modified version of the unified theory model to quantify the damage evolution theoretically. This quantification is representing linearly the damage and giving rise to an accurate approximation of the nondimentional damages. By knowing the constant of each material (maximum pressure, rupture pressure and the rupture pressure of a neat material) we can reproduce the real curves of pressure evolution in function of the life fraction. So, through this method we reduced the number of parameters that must be identified for the thermoplastic materials ’ characterization purpose. 5. Conclusion The use of thermoplastic pipes has been accelerated significantly since its apparition in the 1950s. Thus, many industrial have to choose between the different materials that exist in the market. That’s why in this work , we found a simplified approach to go through HDPE and CPVC behavior toward the burst pressure. Indeed, we chose nondimentional parameters to represent the burst pressure for both the studied materials which have been compared to the theoretical one. Moreover, simplified version of unified theory damage based on burst pressure only have been clarified and detailed. Another aspect of simplification have been approached by using and modifying the Faupel formula to calculate the burst pressure and then evaluate the damage theoretically. These newly developed approaches can be used by industrial and researches to lead quick verifications and checks by only using cost effective static tests instead of dynamic ones.