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Damage of PE-HD due to environmental stress cracking (ESC) induced by liquid media - Full Notch Creep Testing (FNCT)

  • Due to the increasing demand for utilization and improvement of energy efficient materials, especially concerning requirements in lightweight construction and design, polyolefin materials are used extensively and in an increasingly broad range of applications. Although loaded with stresses under yield stress, preformed voids, inhomogeneities or notches can possibly lead to damage and unexpected failure induced by liquid media in polyolefin materials. For PE-HD, slow crack growth (SCG) as well as environmental stress cracking (ESC) are relevant mechanisms of damage. SCG appears without influence of a surrounding medium or in “inert” media whereas ESC occurs in “active” media, which have decisive influence on damage mechanism and time to failure. To characterize the intrinsic resistance of the material against those damage mechanisms, the Full-Notch Creep Test (FNCT) is widely used and of paramount importance particularly for the assessment of pipe and blow molding types of PE-HD. InDue to the increasing demand for utilization and improvement of energy efficient materials, especially concerning requirements in lightweight construction and design, polyolefin materials are used extensively and in an increasingly broad range of applications. Although loaded with stresses under yield stress, preformed voids, inhomogeneities or notches can possibly lead to damage and unexpected failure induced by liquid media in polyolefin materials. For PE-HD, slow crack growth (SCG) as well as environmental stress cracking (ESC) are relevant mechanisms of damage. SCG appears without influence of a surrounding medium or in “inert” media whereas ESC occurs in “active” media, which have decisive influence on damage mechanism and time to failure. To characterize the intrinsic resistance of the material against those damage mechanisms, the Full-Notch Creep Test (FNCT) is widely used and of paramount importance particularly for the assessment of pipe and blow molding types of PE-HD. In this study, the FNCT – usually applied as a standardized testing method (ISO 16770) using a few universal model liquid media – is extended by investigations of selected relevant PE-HD materials with a variety of properties also in real media. Mainly topical fuels, customary in the market such as diesel and biodiesel are examined. Especially the influence of temperature, and the ESC behavior of PE-HD in media that are sorbed to a significant extent, are addressed. The underlying diffusion-controlled sorption process was assessed before comparing non-saturated specimens with samples previously saturated with sorbing media. The investigations were performed using a novel FNCT-device with 12 individual sub-stations, each equipped with individual electronic stress and temperature control and continuous online monitoring of the specimen elongation. In addition to acquired results concerning time to failure and elongation behavior, imaging techniques, such as light microscopy (LM), laser scanning microscopy (LSM) and X-ray computed tomography (CT scan) were utilized to obtain data concerning crack propagation and media migration. Fracture surface analysis (LM, LSM) and quasi in-situ imaging (CT scan) via measurement in different load stages are considered explicitly. Correlations of elongation behavior and data derived from imaging analysis such as fracture plane roughness and height of areas of ductile deformation were obtained.zeige mehrzeige weniger

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  • Presentation_ESC_of_PE-HD_FNCT_EuroCorr2017_BAM_Markus_Schilling.pdf
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Metadaten
Autoren/innen:Markus Schilling
Koautoren/innen:Ute Niebergall, Martin Böhning
Dokumenttyp:Vortrag
Veröffentlichungsform:Präsentation
Sprache:Englisch
Jahr der Erstveröffentlichung:2017
Organisationseinheit der BAM:5 Werkstofftechnik
5 Werkstofftechnik / 5.3 Mechanik der Polymerwerkstoffe
7 Bauwerkssicherheit
7 Bauwerkssicherheit / 7.5 Technische Eigenschaften von Polymerwerkstoffen
DDC-Klassifikation:Technik, Medizin, angewandte Wissenschaften / Ingenieurwissenschaften / Ingenieurwissenschaften und zugeordnete Tätigkeiten
Freie Schlagwörter:Biodiesel; Diesel; Environmental stress cracking (ESC); Full notch creep test (FNCT); High-density polyethylene (PE-HD); Slow crack growth (SCG)
Themenfelder/Aktivitätsfelder der BAM:Material
Material / Degradation von Werkstoffen und Materialien
Veranstaltung:EUROCORR2017
Veranstaltungsort:Prague, Czech Republic
Beginndatum der Veranstaltung:03.09.2017
Enddatum der Veranstaltung:07.09.2017
Verfügbarkeit des Volltexts:Volltext-PDF im Netzwerk der BAM verfügbar ("Closed Access")
Datum der Freischaltung:21.12.2017
Referierte Publikation:Nein