High cycle fatigue and fatigue crack propagation design curves for 5754-H22 and 6082-T6 aluminium alloys and their friction stir welded joints

Friction stir welding (FSW) is a dynamically developing version of pressure welding processes. Nowadays, learning the properties and behaviour of the welded joints is an important direction of investigation, especially under cyclic loading. The research work aimed (i) to demonstrate the behaviour of FS welded joints under cyclic loading conditions and (ii) to determine fatigue design curves for two aluminium alloys and their welded joints made by the FSW process. Experiments were performed on 5754-H22 and 6082-T6 aluminium alloys and their welded joints; high cycle fatigue (HCF) and fatigue crack propagation (FCG) tests were performed. Statistical approaches were applied during the experiments and the evaluation process. HCF design curves were determined based on the staircase method and FCG design curves were determined by our own previously developed six-step method. The results of the HCF and FCG tests on FS welded joints confirm the applicability of the applied FSW technology and show good correspondence with results of the comparative base materials and welded joints that can be found in the literature. Based on our experimental results and the evaluation methods used, statistically established parameters of HCF and FCG design curves were calculated.