The Design of Fatigue Test Machine and the Analysis of Fatigue Behavior of FSWed Dissimilar Aluminum Alloys

Aluminum alloys have low density and high yield strength, thus leading them to be commonly used in aircrafts, sea vessels and land vehicles to acquire light weight and their use in these industries has been increasing every passing day. It is necessary to assemble many dissimilar aluminum alloys in such a way that they fit one another in the application. However, the parts made of these alloys are exposed to very different stresses (tensile, bending, impact, etc.) and fatigue occurs in the parts working especially under dynamic loads by causing structural damage. In this study, a computer-based fatigue test machine was designed and manufactured in order to do the fatigue tests for plate-type materials. This machine was used for the fatigue tests of dissimilar aluminum alloys (AA5754/AA6013) welded by the friction stir welding (FSW). FSW was carried out at 12.5, 25, and 32 mm/min welding feed rates and 1250 rpm. In addition, metallographic examinations and hardness tests were carried out to determine macrostructural and microstructural properties of weld zones and the effects of the joints on fatigue strength. The findings of the tests were evaluated and interpreted. The new machine successfully tested the fatigue of the FSWed samples. It was determined that in FSW, welding feed rate and material type were effective on the heat input, microstructure, hardness distribution of the weld zone and fatigue strength and life of the joints.