Einfluss des Gefüges von explosionsverfestigtem Hadfield-Stahl auf die Ausbreitung akustischer Oberflächenwellen

Translated title of the contribution: Effect microstructure of explosion hardened Hadfield steel on the propagation of surface acoustic waves

Lukas Feichtenschlager

Research output: ThesisMaster's Thesis

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Abstract

More than 25% of all turnout hearts in Austria are made of Hadfield-steel, also known as Mn-13 steel. Due to its cast structure and coarse grains, this steel is not practical for ultrasonic testing. The main goal of this diploma thesis is to examine whether ultrasonic testing in near-surface areas is possible with the use of surface acoustic waves and whether the explosion hardening to which the Hadfield-steel is subjected to extend its service life leads to a change in the propagation of the surface wave. Finally, it should be clarified whether cracks can be detected with the used setup. This smaller wavelength leads to a larger ratio of grain size to wavelength. This ratio is decisive for the type of scattering, which significantly influences the attenuation at room temperature. Velocity of propagation and attenuation coefficient were measured by transmission method for different stages of explosion hardening. For this purpose, optical microscope images were taken near the ultrasonic measurement positions at the rail head and rail foot to determine the grain size. In addition, the specimens were subjected to a hardness progression test. The explosion hardening leads to an increase in hardness near the surface. It was demonstrated that the attenuation coefficient of Rayleigh waves due to explosion hardening decreases significantly for measurement frequencies on rail specimens of 1 and 2 MHz at the rail head. This is due to a decrease in scattering, which is also provable at the rail foot that is also deformed plastically when explosion hardening of turnouts. For measurements with frequencies of 2 MHz, a trend towards a decrease in propagation velocity due to explosion hardening can be observed, the exact clarification of which requires further investigations. It has been shown that crack detection with surface waves is possible at the Hadfield- steel and the crack can lead to a reduction in amplitude and propagation delay of the wave.
Translated title of the contributionEffect microstructure of explosion hardened Hadfield steel on the propagation of surface acoustic waves
Original languageGerman
QualificationDipl.-Ing.
Awarding Institution
  • Montanuniversität
Supervisors/Advisors
  • Eck, Sven, Co-Supervisor (internal)
  • Ebner, Reinhold, Supervisor (internal)
Award date17 Dec 2021
Publication statusPublished - 2021

Bibliographical note

no embargo

Keywords

  • Ultrasonic-testing
  • Hadfield Steel
  • Surface Acoustic Waves

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