Filtern
Erscheinungsjahr
- 2016 (4) (entfernen)
Dokumenttyp
- Zeitschriftenartikel (1)
- Beitrag zu einem Tagungsband (1)
- Vortrag (1)
- Posterpräsentation (1)
Schlagworte
Eingeladener Vortrag
- nein (1)
Nondestructive flaw detection in polymeric materials is important but difficult to achieve. In this research, the application of magnetite nanoparticles (MNPs) in nondestructive flaw detection is studied and realized, to the best of our knowledge, for the first time. Superparamagnetic and highly magnetic (up to 63 emu/g) magnetite core-shell nanoparticles are prepared by grafting bromo-end group-functionalized poly(glycidyl methacrylate) (Br-PGMA) onto surface-modified Fe3O4 NPs. These Fe3O4-PGMA NPs are blended into bisphenol A diglycidylether (BADGE) based epoxy to form homogeneously distributed magnetic epoxy nanocomposites (MENCs) after curing. The core Fe3O4 of the Fe3O4-PGMA NPs endows the MENCs with magnetic property, which is crucial for nondestructive flaw detection of the materials, while the shell PGMA promotes colloidal stability and prevents NP aggregation during curing. The eddy current testing (ET) technique is firstly applied to detect flaws in the MENCs. Through the brightness contrast of the ET image, surficial and sub-surficial flaws in MENCs can be detected, even for MENCs with low content of Fe3O4-PGMA NPs (1 wt %). The incorporation of Fe3O4-PGMA NPs can be easily extended to other polymer and polymer-based composite systems and opens a new and very promising pathway toward MNP-based nondestructive flaw detection in polymeric materials.
For non-destructive testing (NDT) appropriate reference blocks are required in order to verify and calibrate a testing procedure. At BAM a special electric discharge machining (EDM) system has been developed which is able to manufacture artificial defects having a width down to 30 μm.
Especially in the case of austenitic materials conventional EDM leads to a transformation of austenite to martensite. The martensite transformation causes a higher sensitivity of electromagnetic NDT methods (e. g. eddy current testing) at the artificial defects compared to natural defects of same size. The EDM system developed at BAM uses very low energy to avoid this material transformation. A side effect of the low-energy EDM is a lower surface roughness compared to conventional EDM. The artificial defects manufactured at BAM are measured optically and delivered with a certificate. A comparison of artificial defects shows the influence of material transformation on NDT and how differently the quality of the artificial defects can be.
For non-destructive testing (NDT) appropriate reference blocks are required in order to verify and calibrate a testing procedure. At BAM a special electric discharge machining (EDM) system has been developed which is able to manufacture artificial defects having a width down to 30 μm.
Especially in the case of austenitic materials conventional EDM leads to a transformation of austenite to martensite. The martensite transformation causes a higher sensitivity of electromagnetic NDT methods (e. g. eddy current testing) at the artificial defects compared to natural defects of same size. The EDM system developed at BAM uses very low energy to avoid this material transformation. A side effect of the low-energy EDM is a lower surface roughness compared to conventional EDM.
The artificial defects manufactured at BAM are measured optically and delivered with a certificate.
A comparison of artificial defects shows the influence of material transformation on NDT and how differently the quality of the artificial defects can be.
Ausgehend von einer Machbarkeitsstudie im Jahr 1999 wurde von der BAM in Zusammenarbeit mit der DB AG und verschiedenen anderen Partnern ein Schienenprüfsystem zur Detektion und Bewertung von Schienenfehlern des Typs Head Checks entwickelt. Dieses Prüfsystem arbeitet nach dem Wirbelstromprinzip. Die Firma Prüftechnik Linke & Rühe GmbH aus Magdeburg fertigt und vertreibt seit geraumer Zeit verschiedene manuelle und zuggestützte Prüfsysteme, die auf dieser Entwicklung basieren. Seit Januar 2013 wird in Deutschland der Qualitätsnachweis nach der Schienenbearbeitung mittels Wirbelstromprüfung gefordert.
Im Laufe der Entwicklungsarbeiten wurden verschiedentlich benachbarte Themenfelder rund um die Prüfung auf Head Checks gestreift. Der Schwerpunkt dieses Vortrages liegt auf diesen erweiterten Möglichkeiten der magnetinduktiven Prüfung von verlegten Schienen. Hierbei wird sowohl auf die Verbesserung der Möglichkeiten des bestehenden Systems (z. B. durch Kopplung mit anderen Prüfverfahren) als auch auf mögliche Neuentwicklungen (z. B. durch Einsatz neuer Sensorik) eingegangen. Angestrebte Ziele sind z. B. die Verbesserung der Prüfaussage bei der Head Check Prüfung, Erweiterung der Prüfaussage auf andere Schienenfehlertypen oder die Bestimmung von Schieneneigenschaften wie Härte und Rauigkeit.