A simple method, based on the fracture mechanics stress intensity factor K approach, is proposed to predict the lifetime of a polyethylene pipe subject to constant internal pressure for discontinuous crack propagation. Two distinct relationships, Knv.time to initiation tin and Knv.crack extension Deltaan, must be determined. Attemps to derive these relationships from linear visoelastic fracture theories lead to contradictory results, which have been attributed to some inadequacy of the Dugdale-Barenblatt model to account for the process zone size of these materials. Linear viscoelastic fracture theories may be inadequate because of the non-linear behaviour of the material during fracture or the presence of a fully yielded ligament at certain stages of crack advancement. New process zone models appear to be more appopriate for the prediction of the fracture behaviour in such materials. The results of one model of them were found to agree at least qualitatively with the present results and further work is in progress.
Discontinuous creep crack growth in polyethylene
Plastics, Rubber and Composites Processing and Applications ; 25 , 5 ; 221-225
1996
5 Seiten, 9 Bilder, 17 Quellen
Aufsatz (Zeitschrift)
Englisch
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