Prediction of the residual strength of corroded high-strength aluminum alloys under uniaxial loading by numerical simulations

• Applicants: Professor Dr.-Ing. Thomas Lampke; Professorin Dr.-Ing. Daniela Nickel
• Subject Area: Mechanical Properties of Metallic Materials and their Microstructural Origins
• Term: from 2014 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 259373824

High-strength aluminum alloys are used in a variety of components due to their high strength and good corrosion resistance. However, the corrosion resistance will fail if the passive layer is damaged, e.g. by chloride ions. Local corrosion phenomena (henceforth referred to as defects) and pitting corrosion occur as the damage is proceeding. This leads to a strength reduction of the material. The residual strength prediction under an uniaxial tensile loading based on the state of pitting corrosion is, thus far, not state of the art for high-strength aluminum alloys. The aim of this research project is the prediction of residual strength by a standard surface inspection. Two aluminum alloys (EN AW-2xxx and EN AW-7xxx) are carried out to transfer existing prediction models for steels to the high-strength aluminum alloys. The existing models will be improved by observing the morphology and distribution of the occurring defects. Corrosion tests at different conditions are realized to develop the model. The gained pitting corrosion will be quantified for each sample by using parameters to describe the shape and the distribution of the defects. The characterization of the defects will be non-destructive using a micro-optical 3D pattern surface measuring device. Subsequent FE-simulations of tensile tests are executed to attain analytical relations between the defect shape, distribution and residual strength. This will be achieved by means of a regression analysis. Additionally, stress analyses are performed to discuss critical defect shapes and distributions. This will be implemented by weighting factors. Finally, the residual strength model is obtained by the analytical relations and the weighting factors. The independent material reduction factor will be calculated by relating the calculated strength of the current damage state to the strength of the non-corroded material. Thus, the model to predict the residual strength can be applied to further aluminum alloys.

• DFG Programme: Research Grants