Description
Friction-welded joints can be found in a whole range of technical applications, such as in mechanical engineering in series production of gears, lifting rods, gear parts and shafts but also in apparatus and steel construction on pipes, flanges and anchorages. The rotary friction welding is characterized by a high efficiency due to the short cycle time, high constant quality and reproducibility.
The fatigue strength is a decisive criterion for security relevant friction-welded joints and requires particular attention. Currently, there is no validated calculation concept for the assessment of the fatigue strength of friction-welded joints available. Fatigue design values are determined experimentally by investing a lot of time and examination effort. The result is a long product development time and burden especially small and medium-sized enterprises because of their limited test capabilities. Classical concepts for the assessment of the fatigue strength of welded joints, such as the nominal, structural and notch stress concepts were derived for fusion- and resistance-welded joints and do not take into account the microstructural and geometrical characteristics of friction-welded joints. Furthermore rotary-friction-welded joints form a welding bead, which is removed in practice partially and thus sometimes the joints have no geometrical notch.
The aim of this project is to extend the classical calculation concepts (nominal and notch stress concept) to the applicability to friction-welded joints and to develop a concept for the assessment of the fatigue strength based on local strain approach. The basis is formed by extensive fatigue strength tests, which are accompanied by numeric investigation.
