Einfluss der Randschicht auf die Ermüdungsfestigkeit additiv gefertigter Aluminiumbauteile

Translated title of the contribution: Effect of surface layer on the fatigue strength of additively manufactured aluminium components

Sebastian Springer

Research output: ThesisMaster's Thesis


Additive Manufacturing is increasingly gaining importance in the production of components. An important factor for the application of additive manufacturing for failure-critical structural components is sufficient knowledge on the influence of local material properties on fatigue strength. In this thesis the influence of the surface condition as well as the effect of thermal post-treatment processes on the fatigue strength of additively manufactured aluminium components are investigated. Especially in case of geometrically complex AM structures, mechanical surface treatment is only possible to a limited extent, whereby an evaluation of the unprocessed rough surfaces is decisive. For the investigations, round aluminium samples were manufactured with selective laser melting by the industrial partner, whereby test series with different thermal post-treatments as well as another series in as-built condition were investigated. In addition, from each series samples with a polished and a rough surface were analysed. The surface of the as-built samples was scanned with a digital light microscope to characterize the surface topography in detail and to determine common surface parameters. The subsequent cyclic tests were performed at a stress ratio of R=-1 on a resonance testing machine. Accompanying, a comprehensive damage analysis of the fracture surface was carried out using optical light microscopy. It was shown that both hot isostatic pressing (HIP) and T6 heat treatment have a positive effect on the long-life fatigue strength in the polished condition with an increase by up to 14% and 6% respectively compared to the as-built condition. The cyclic tests with the rough specimens showed a reduction in fatigue strength of about 60% compared to polished specimens. In order to assess the micro-notch effect of rough surfaces, a stress concentration factor was determined considering selected surface parameters for each sample series. Applying this factor, the reduction of the fatigue strength was estimated, which reveals a sound correlation with the experimental results. Finally, the experimentally evaluated fatigue strength of AM specimens within the scope of this work was matched with values of comparable aluminium casting specimens from the literature, whereby the modern AM process results are about 30% higher than the values of conventional casting technology. In summary, it can be stated that a rough surface significantly reduces the fatigue strength of additive manufactured samples. However, it is possible to increase the long life fatigue strength again by thermal post-treatment. For the holistic evaluation of the fatigue strength of AM components and the influence of the rough surface, the consideration of further technological influencing factors and their interactions must be included in future investigations.
Translated title of the contributionEffect of surface layer on the fatigue strength of additively manufactured aluminium components
Original languageGerman
Awarding Institution
  • Montanuniversität
  • Grün, Florian, Supervisor (internal)
  • Leitner, Martin, Co-Supervisor (internal)
Award date12 Apr 2019
Publication statusPublished - 2019

Bibliographical note

embargoed until 12-03-2024


  • additive manufacturing
  • selective lasermelting
  • fatigue
  • surface roughness
  • heat treatment
  • AlSi10Mg

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