Klochkov I. Fatigue improvement of welded joints of thin aluminium alloys with ultrasound impact treatment

Candidate's thesis in specialty 05.03.06 "Welding and related processes and technologies". E.O. Paton Electric Welding institute of NAS of Ukraine, Kiev, 2013. The thesis covers experimental investigation of conformities of fatigue resistance welded joints of thin (2…3 mm) high and medium strength aluminium alloys produced with MIG-Pulse welding as well as their fatigue improvement using Ultrasound Impact Treatment (UIT). The investigations of technological features of MIG-Pulse butt-welded joints of aluminium alloy D16T, AMg6 and 6061 (2 mm thick) are presented as well as 2 and 3 mm thick overlap welds. The influence of welding parameters on geometrical parameters, microstructure and mechanical properties of welds is shown. The recommendations to welding technology for acquiring high quality weldments are provided. The influence of structural eccentricity and the size of overlap on fatigue performance of thin overlap welded joints of MIG-Pulse welded aluminium alloys AMg6 and 6061 has been experimentally shown in the work. Application of UIT to weld notch zones is proposed as the method of cold straightening for decreasing of structural eccentricity and increase of fatigue performance. Treatment parameters are selected to insure the misalignment angle close to zero. It is shown that UIT of weld notch zones of two corner welds of thin overlap welds of aluminium alloys under investigation leads to an increase of limited durability on the base 106 load cycles by 30 times during pulse loading.