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The magnitude of different aluminium alloys, especially the ones with higher strength, are increasing in the structural engineering, not just the usual applications (like the aerospace industry) but more likely in the automotive industry. There are more assumptions of the effective use of aluminium; we should highlight two important factors, the technological and the applicability criterions. The technological criterion is the joining of structural elements, frequently with welding thus the technological criterion ultimately is the weldability. The assumption of applicability comes from the loading capability of these structures, which is typically cyclic loading so the key issue from the point of view of applicability is the resistance to fatigue. This article represents physical simulation and fatigue test results both on the base material and on the welded joints.

The usage of modern high strength aluminium alloys are getting more remarkable in several industry sectors mostly the fabrication of light weight structures, such as vehicles, railway transport systems, aerostructures and building constructions. The weldability problems of these alloys are more complex than the steels with similar strength. Therefore weldability problems must be analyzed very accurately, by the help of the modern physical simulation. By knowing the difficulties of the weldability of high strength aluminium alloys the proper parameters of the welding technology can be defined. This article represents the investigation of a certain weldability problem of 6082T6 aluminium alloy with the aim of physical simulation and welding experiments with gas metal arc welding and pulsed current technology.

Our research work has focused from the materials world on the aluminium alloys, from the manufacturing processes on the welding technologies, and from different loads on the cyclic loads. The article aimed (i) to demonstrate the behaviour of the friction stir welded (FSW) joints under cyclic loading conditions; (ii) to determine fatigue (limit) curves for two aluminium alloys and their welded joints. Experiments were performed on 5754-H22 and 6082-T6 aluminium alloys and their FSW joints. Both high cycle fatigue (HCF) and fatigue crack propagation (FCG) tests were executed on both base materials and their welded joints. Statistical behaviour of the base materials and welded joints was represented by the cutting of the specimens and the using of different crack paths. HCF limit curves were determined based on staircase method and FCG limit curves can be determined by own developed six step method. The investigations and their results were compared with each other and with the results can be found in the literature.