Modification of a defect-based fatigue assessment model for Al-Si-Cu cast alloys

Roman Aigner, Martin Leitner, Michael Stoschka, Christian Hannesschläger, Thomas Wabro, Robert Ehart

Research output: Contribution to journalArticlepeer-review

14 Citations (Scopus)

Abstract

Cast parts usually inherit internal defects such as micro shrinkage pores due to the manufacturing process. In order to assess the fatigue behaviour in both finite-life and long-life fatigue regions, this paper scientifically contributes towards a defect-based fatigue design model. Extensive fatigue and fracture mechanical tests were conducted whereby the crack initiating defect size population was fractographically evaluated. Complementary in situ X-ray computed tomography scans before and during fatigue testing enabled an experimental estimation of the lifetime until crack initiation, acting as a significant input for the fatigue model. A commonly applied fatigue assessment approach introduced by Tiryakioglu was modified by incorporating the long crack threshold value, which additionally enabled the assessment of the fatigue strength in the long-life fatigue regime. The presented design concept was validated utilising the fatigue test results, which revealed a sound agreement between the experiments and the model. Only a minor deviation of up to about five percent in case of long-life fatigue strength and up to about 9% in case of finite-lifetime were determined. Thus, the provided extension of Tiryakioglu's approach supports a unified fatigue strength assessment of cast aluminium alloys in both the finite- and long-life regimes.

Original languageEnglish
Article number2546
JournalMaterials
Volume11
Issue number12
DOIs
Publication statusPublished - 14 Dec 2018

Keywords

  • Aluminium casting
  • Computed tomography
  • Defects
  • Extreme value statistics
  • Fatigue assessment
  • Statistical distribution

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