Die Auswirkung von gussrauen Oberflächen auf die Schwingfestigkeit von gegossenem Aluminium im Automobilbau

Translated title of the contribution: The effect of rough aluminium casting surface on fatigue life exemplified for automotive components

Matthias Aigner

Research output: ThesisMaster's Thesis


The need for a load dependent design process of casted aluminium structures has recently increased in the automotive industry. Parts like this are nowadays often fabricated through dead-mould casting and feature high potential for lightweight constructions. It is their purpose to reduce pollutant emission of combustion engines by reducing weight. These complex parts enforce innovative sand casting techniques. An example is the “Core-Package-System” which allows for near net shape production of castings. The resulting roughness and topography of the surfaces are severely influenced by the production process and the used mould. In real automotive engineering applications both, the comparably rough as-casted as well as the machined surface condition, are used. This thesis deals with the effect of untreated rough casting surface on the fatigue life. One key point is to define a specimen shape which represents the automotive series production process most accurately. To make sure that the conducted tests are in line to the series manufacturing casting process, the specimens itself are designed as flat samples which are fabricated directly from series production crankcases. These samples exhibit a rough casting surface on one side which is hence characteristic for the industrial casting process. These specimens fatigued by sinusoidal constant amplitude testing in both, alternating tension-compression and tumescent bending mode. To assess the local influence of the surface topography, a numerical analysis based on notch stresses is conducted. Therefore, the surface of the casted part is optically scanned with a confocal microscope. The result is a three dimensional topography of the surface which is subsequently used to set up a finite element model. Tension-compression and shear loadings in numerical simulation runs, lead to multiaxial stress distributions which show local stress peaks in valleys on the meshed surface. By the use of the fracture mechanical, long crack growth threshold of the defect free aluminium in conjunction with critical distance theory as fatigue approach it is possible to evaluate fatigue notch factors. This novel procedure for casted surfaces enables an assessment of the influence of surface roughness and topography under cyclic loading. Findings from the experimental Wöhler fatigue tests are further opposed to the numerically evaluated factors, which allow a validation of the fatigue limits of differently rough surfaces reflecting variations in the casting process. The methodology which is introduced in this thesis enables an enhanced local insight in the influences of surface topography on fatigue life of casted aluminium parts as well as their interaction with possible imperfections in the surface layer. This enables an improved design chain which focuses on optimization of complex aluminium castings towards fatigue strength and local manufacturing conditions. Therefore it is possible to reduce costs of material testing and shorten the spent time on development and design of aluminium castings in automotive applications.
Translated title of the contributionThe effect of rough aluminium casting surface on fatigue life exemplified for automotive components
Original languageGerman
  • Leitner, Martin, Co-Supervisor (internal)
  • Stoschka, Michael, Supervisor (internal)
Award date21 Oct 2016
Publication statusPublished - 2016

Bibliographical note

embargoed until 08-09-2021


  • aluminium
  • casting
  • surface roughness
  • fatigue strength

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