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Morphological and Structural Effects on Slow Crack Growth in PE-Pipes [PE]

 

Additional Information - Posters # 2006 Washington DC

Slow crack growth (SCG) was measured by means of an adaptive to the Full Notch Creep Test (FNCT) : the 2-Notch Creep Test (2NCT). This notching geometry offers the advantage, that the sensitive zones of samples made of pipe specimens are conserved : the inner- and outer-pipe wall layers. This test geometry makes it possible to achieve fracture results including the sensitive regions with the highest internal-stresses and orientations. Fracture results on a DN 315x17,9 PE100 pipe of a bimodal PE100 compound show, that the outer-pipe wall specimens have the shortest times to failure. To the inner-pipe wall section the failure times increase. As reference a 6 mm thick compression moulded sheet with slow cooling rate was produced of the same material. Samples of the sheet show the highest failure time. The different failure times can be related to morphological- and structural-effects but furthermore investigations are necessary. It was shown in samples investigated prior total fracture that there is a complex fracture behaviour evident in pipe specimens due to morphological- and structural-effects with partial secondary crackinitiation points, which leads to the different failure times of the pipe wall sections.

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