Mechanische und Thermomechanische Ermüdungseigenschaften von wärmebehandelten Aluminium-Silizium Gusslegierungen

Translated title of the contribution: Mechanical and Thermo-Mechanical Fatigue Properties of heat-treated Aluminium-Silicon cast alloys

Patrik Huter

Research output: ThesisDoctoral Thesis


A combustion engine's cylinder head is faced with complex loadings during operational condition. This is due to the interaction between the complex geometric geometry, which is founded by its manifold functions, and the transient anisothermal operational loadings. Furthermore, the engine's lifetime is greatly determined by the reliability of the cylinder head itself. Hence, a detailed and unified theory including quantitative descriptions of the inherent damage mechanisms under operational conditions is necessary. This allows the cylinder head manufacturer to develop specific new alloy combinations with improved fatigue properties during operation, while at the same time helping the costumer to interactively optimize mechanical and thermal boundary conditions with respect of the material. In this thesis, a unified fatigue model is developed to describe quantitatively realistic damage. Hence, eight different aluminium-silicon cast alloys with T79 heat treatment were analyzed using different fatigue tests. The thermo-mechanical fatigue test with its inherent anisothermal and plastic loading simulates real component damages, as oxidation is not relevant here for TMF endurance. Supplementary isothermal fatigue tests and microstructural crack analysis aided the quantification of the characteristic damages. Between high and low copper alloys, different damage mechanisms were found and reflected in changes of the TMF endurances up to a factor of two. The ductility is mainly determined by the precipitation hardening of intrinsic copper. Silicon deflects the crack paths and decreases the crack growth rate; therefore fatigue lifetime increases. In high plasticity regimes cracks are generated in such a high number that they are not significant for quantitative fatigue lifetime anymore. Based on these and additional observations, a damage model was created, which takes all these effects under ambient conditions and temperature related fatigue into consideration. Hence, with only one parameter set all aluminium-cast alloys were calculated in different loading regimes. Further, they were compared with the TMF model based on Neu & Sehitoglu and a neuronal damage model. A specially programmed TMF post-processing tool allowed the implementation in finite element software. Its application on a demonstration cylinder head showed different hot spots of damage for each model. Thus, further tests on real components are recommended for validation.
Translated title of the contributionMechanical and Thermo-Mechanical Fatigue Properties of heat-treated Aluminium-Silicon cast alloys
Original languageGerman
  • Grün, Florian, Assessor A (internal)
  • Ebner, Reinhold, Assessor B (internal)
Publication statusPublished - 2016

Bibliographical note

embargoed until 26-01-2021


  • cylinder head
  • thermo-mechanical fatigue
  • aluminium
  • damage analysis
  • fatigue
  • lifetime
  • fatigue model
  • TMF
  • LCF
  • HCF
  • Al-Si cast alloy

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