Determination of the mechanical behavior of thin walled welded and adhesively bonded structures

The widespread use of thin-walled circular cross-section hollow structures in drive shafts, engine valves, pipelines and various components in many areas of the automotive industry, construction and marine sectors is increasing day by day. Many factors contribute to this increase, such as cost and weight economies and the development of new materials and analysis methods. In the automotive industry, the use of thin-walled circular cross-section pipes brings great advantages in terms of both cost and light weight. The high performance, fuel efficiency and environmental features such as low carbon emissions required in today's vehicles also emphasize the use of composite materials that provide high strength and rigidity despite alternative low density in power and motion transmission applications. Regardless of the application, whether it is a thin-walled metal-to-metal connection or a thin-walled metal-composite material connection, the connection region appears to be the weakest aspect of the structure. This study, in which the thin-walled tube connection with the tube fork, which is a part of the fixed cardan joint, which is a sub-assembly of the cardan shafts, which are widely used as power transmission elements in land vehicles, is selected as an application example, consists of two stages. In the first stage, the weldability of two different thin-walled steel materials by friction welding, a solid-state joining method, and the mechanical properties of the welded joint were investigated. The torsional load carrying capacities of friction welded thin-walled cold drawn welded tube and micro alloy tube fork joints were determined by static torsion test and the torsional fatigue behavior of the joints were determined by full wave full alternating fatigue tests at different torsional load levels determined from vehicle field data. In the second stage of this study, a hollow tube (metal adapter) of circular cross-section manufactured using unalloyed reclaimed steel, joined with two-component acrylic adhesive, and a carbon fiber reinforced composite tube manufactured using filament winding technique, representing the connection between the tube fork, which is part of the fixed cardan joint, and the thin-walled tube. Torsional load carrying capacity of carbon fiber reinforced composite tube and adhesive joints are defined by numerical methods. In addition, the torsional load carrying capacities were determined by static torsion test, and the torsional fatigue behavior of the connections was determined with the help of bi-directional fatigue tests at a specific torsional load level which was derived from vehicle field data. As a result, according to the data obtained for both connection types, the pros and cons of the welded design, which is used in the field in practice, and the composite-metal bonded connection design that can be used industrially, and their performance on the vehicle effects are discussed.