Fatigue improvement of aluminium welds by means of deep rolling and diamond burnishing

Deep rolling is an industrially widely established mechanical surface treatment process for the modification of roughness and fatigue resistance. However, the process has not been considered as a potential method for the mechanical post welded treatment of welded joints yet. Even, the potential of deep rolling for increasing the fatigue strength is comparably well-known in the case of non-welded components. Therefore, the effect of deep rolling (hydrostatic mounted tool) and diamond burnishing (mechanical mounted tool) to increase the fatigue strength of butt joints was approved in this work for aluminium alloy AlMg4,5Mn0,7 (EN AW 5083). For this purpose, fatigue tests under full tensile loading were performed in as-welded and deep rolled, burnished and ultrasonic impact treated conditions. Different residual stress states as well as work hardening states are determined in deep rolled and burnished condition. However, similar and significant fatigue life improvement was determined for both processes.