Accelerated Testing Method to Estimate the Lifetime of Polyethylene Pipes

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dc.contributor.authorKalhor, Roozbehen
dc.contributor.committeechairCase, Scott W.en
dc.contributor.committeememberBaird, Donald G.en
dc.contributor.committeememberBortner, Michael J.en
dc.contributor.departmentMacromolecular Science and Engineeringen
dc.date.accessioned2017-11-02T20:48:44Zen
dc.date.adate2017-06-26en
dc.date.available2017-11-02T20:48:44Zen
dc.date.issued2017-02-14en
dc.date.rdate2017-06-26en
dc.date.sdate2017-02-28en
dc.description.abstractThe ability to quickly develop predictions of the time-to-failure under different loading levels allows designers to choose the best polymeric material for a specific application. Additionally, it helps material producers to design, manufacture, test, and modify a polymeric material more rapidly. In the case of polymeric pipes, previous studies have shown that there are two possible time-dependent failure mechanisms corresponding to ductile and brittle failure. The ductile mechanism is evident at shorter times-to-failure and results from the stretching of the amorphous region under loading and the subsequent plastic deformation. Empirical results show that many high-performance polyethylene (PE) materials do not exhibit the brittle failure mechanism. Hence, it is critical to understand the ductile mechanism and find an approach to predict the corresponding times-to-failure using accelerated means. The aim of this study is to develop an innovative rupture lifetime acceleration protocol for PE pipes which is sensitive to the structure, orientation, and morphology changes introduced by changing processing conditions. To accomplish this task, custom fixtures are developed to admit tensile and hoop burst tests on PE pipes. A pressure modified Eyring flow equation is used to predict the rupture lifetime of PE pipes using the measured mechanical properties under axial tensile and hydrostatic pressure loading in different temperatures and strain rates. In total, the experimental method takes approximately one week to be completed and allows the prediction of pipe lifetimes for service lifetime in excess of 50 years.en
dc.description.degreeMaster of Scienceen
dc.identifier.otheretd-02282017-153621en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-02282017-153621/en
dc.identifier.urihttp://hdl.handle.net/10919/79944en
dc.language.isoen_USen
dc.publisherVirginia Techen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectsmall angle X-ray scattering (SAXS)en
dc.subjectdigital image correlation (DIC)en
dc.subjecttime-temperature superpositionen
dc.subjectductile failureen
dc.subjectplastic pipeen
dc.subjectlong-term hydrostatic strength (LTHS)en
dc.subjectcreep characterizationen
dc.subjectwide angle X-ray diffraction (WAXD)en
dc.titleAccelerated Testing Method to Estimate the Lifetime of Polyethylene Pipesen
dc.typeThesisen
dc.type.dcmitypeTexten
thesis.degree.disciplineMacromolecular Science and Engineeringen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.levelmastersen
thesis.degree.nameMaster of Scienceen

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