Plastic Pipes Conference Association # 2001 Munich
Leevers, Moreno, Paizis
The resistance of PE pipes to rapid crack propagation depends strongly on temperature. The critical pressure measured using ISO 13477 ‘S4’ tests increases abruptly above a transition temperature Tc. For PE100 grades Tc has become a primary index of quality : it must remain below 0°C despite a tendency to increase with, amongst other parameters, pipe size. A method for extrapolating S4 data to pipe sizes which cannot yet be tested is therefore of great practical interest. Three point bend impact fracture tests show an analogous transition, whose temperature Tdb, though just as geometry dependent, has been shown by Clutton to be equal to Tc under specific conditions. This paper demonstrates that Tdb, and its thickness dependence, may itself be predictable from a more basic measurement of shear lip resistance made using a modified impact bend test. Other shear lip resistance results show that large plastic strains can increase or decrease Tdb.
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