Entwicklung einer Umlaufbiege-Prüfmaschine für die In-situ Untersuchung der Rissinitiierung und des mikrostrukturellen Rissfortschritts

Translated title of the contribution: Development of a rotating bending testing machine for the in-situ analysis of crack initiation and microstructural crack growth

Patrik Huter

Research output: ThesisDiploma Thesis

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Abstract

The present diploma thesis deals with the realization of a rotating bending fatigue testing machine, which analyzes in-situ crack initiation and crack growth with the help of a confocal laser reflected light microscope. For this, a standard rotating bending specimen with a diameter of 4 mm was used. This setup facilitates examining the behaviour of short crack growth of various materials such as steel, ductile iron and titanium with respect to grain structure. It can also be transformed into a mounting stage for a scanning electron microscope, thus enabling analysis of any open cracks on the surface of the specimen. To begin with, different construction types were compared with each other to find the most suitable assembly for this purpose. The electrical and mechanical design plans, according to which the machine was constructed, were created keeping in consideration the calculated strength of the materials and safety regulations. The machine is operated by an optimized user-friendly software. During the start-up phase, trials were conducted using austempered ductile iron (ADI). They delivered excellent results in terms of accuracy, simplicity and rapidity. In addition, the thesis includes a fracture mechanical evaluation and discussion of the findings of the tests with ADI. They showed that the microstructural cracks were initiated on the nodular graphite at he surface within the initial 10% of the load cycles to rupture. With progressing fatigue, the sub-surface cracks which primarily originated in vicinity of the underlying nodular graphite, began to appear on the surface.
Translated title of the contributionDevelopment of a rotating bending testing machine for the in-situ analysis of crack initiation and microstructural crack growth
Original languageGerman
QualificationDipl.-Ing.
Supervisors/Advisors
  • Eichlseder, Wilfried, Supervisor (internal)
Award date8 Apr 2011
Publication statusPublished - 2011

Bibliographical note

embargoed until 01-04-2014

Keywords

  • crack
  • rotating bending fatigue
  • confocal
  • reflected light microscope
  • crack initiation
  • testing machine
  • ADI
  • development
  • safety regulations
  • Austempered Ductile Iron

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