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Ultrasonic distinction between oxide inclusions and porosity defects in steel
2003 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

Background In the steel making process, hidden defects of different type, composition, geomerty and size contaminate the resulting solidified material. Ultrasound has been used with success to detect theese defects. As the techical borderlines move ahead, a wish to distinguish between different types of defects with the aid of ultrasound has come through. The research discipline includes signal processing, pattern recognition, mathematical and condensed matter physics and materials technology. Goal, Model and Results The goal of the diploma work has been to investigate the possibility to distinguish between oxide inclusions and porosity. By sampling the lightly damped signal from a piezo-electrical transducer, submerged in water, acting as both the sender of the outgoing pulse and receiver of the echoes of mechanical vibrations with a carrier frequency of 10 MHz in an oscilloscope and analysing the resulting wave packet shape, the data is divided into four groups. From the theory of condensed matter physics a mathematical model is synthesised from the elastic features of the defects. The model approximates the signal with a Fourier-series of four frequency components comprising the outgoing initial wave packet. The interaction with the defect is through an inversion of each frequency component, a frequency and compressibility dependent phase angle, a derivation with respect to time for each frequency component and a scaling. The model recreates wave packets with the main differences between wave packets from porosity and oxide inclusions. The obility of distinction between oxide inclusions and porosity is explained mainly through the great difference in compressibility between the two defect types.The thesis also includes a wave packet catalogue of the data, a verification of correlation between wave packets from oxide inclusions and its model wave packet through a SEM (scanning electron microscope) analysis. The thesis also includes a generalisation of the result and a discussion of further investigations.

Place, publisher, year, edition, pages
2003.
Keyword [en]
Technology, Ultrasonic, Phase Angle, Steel Defects, Oxide Inclusion, Porosity, Equivalent Circuit Theory, Frequency Component, Compressibility
Keyword [sv]
Teknik
Identifiers
URN: urn:nbn:se:ltu:diva-53749ISRN: LTU-EX--03/061--SELocal ID: ac1755e0-e415-421c-bff5-c9078aa1e8b3OAI: oai:DiVA.org:ltu-53749DiVA: diva2:1027125
Subject / course
Student thesis, at least 30 credits
Educational program
Engineering Physics, master's level
Examiners
Note
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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CiteExportLink to record
Permanent link

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Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf