Accelerated Testing Method to Estimate the Lifetime of Polyethylene Pipes

Simple item page
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.abstractgeneralSteel, cast and galvanized iron, and asbestos cement (AC) pipelines have been historically used in water management services. However, they often experienced deterioration because of corrosion and encrustation, resulting in 23 to 27 bursts per 100 miles of pipeline in the US per year. Therefore, plastic pipes were developed to carry liquids (water and sewage), gases, etc. The Plastic Pipe Institute (PPI) requires a service life of at least 50-years for plastic pipes. Hence, pipe producers and material suppliers continuously attempt to improve the materials and manufacturing processes used for plastic pipes to increase their service lifetimes. However, there is still no plastic pipe that has been in service for 50 years. Therefore, a few techniques have been developed to accelerate the aging process and to predict if the plastic pipe is able to endure the 50-year lifetime without failure. In this work, a combined experimental and analytical framework is presented to develop accelerated lifetime estimates for plastic pipes. Custom axial tensile and internal pressurization fixtures are developed to measure the pipe response; the analytical method is used to extend the results to predict 50-year (and beyond) behavior.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

Files

Original bundle
Now showing 1 - 1 of 1
Thumbnail Image
Name:
etd-02282017-153621_Kalhor_R_T_2017.pdf
Size:
2.26 MB
Format:
Adobe Portable Document Format
Description:
Download

Collections

Masters Theses