The Paton Welding Journal, 2013, #3, 51-53 pages
IMPROVEMENT OF FATIGUE STRENGTH OF OVERLAP JOINTS OF SHEET ALUMINIUM ALLOYS MADE BY FUSION WELDING
V.V. KNYSH, I.N. KLOCHKOV and I.V. BEREZIN
E.O. Paton Electric Welding Institute, NASU, Kiev, Ukraine
Overlap joints have the advantage of simplicity of their preparation and fit-up for welding, however, because of a number of technological factors, they are characterized by low values of cyclic fatigue life. The influence of structural eccentricity and overlap value on fatigue strength of overlap welded joints of sheet aluminium alloys AMg6 and 6061-T6 made by consumable electrode gas-shielded pulsed-arc welding was shown experimentally. Application of high-frequency mechanical peening of the zones of weld-to-base metal transition was proposed as cold straightening technique to lower the values of structural eccentricity and improve the values of welded joint fatigue strength. Low-intensity high-frequency peening from one side results in plastic deformation of the surface metal layer in the treatment zone, leading to formation of a system of residual stresses, the impact of which causes bending-out in the joint plane. Treatment mode is selected so that the angle of misalignment relative to load application in the treated joints was close to zero. It is found that strengthening by high-frequency mechanical peening of fillet sections of fusion zones of two fillet welds in sheet overlap joints of the studied aluminium alloys leads to increase of their limited fatigue limits on the base of fatigue lives from 5р103 up to 106 cycles of stress alternation, thus increasing their cyclic fatigue life up to 30 times at zero-to-tension loading. 10 Ref., 4 Figures.
arc welding, sheet aluminium alloys, overlap welded joints, fatigue strength, structural eccentricity, high-frequency mechanical peening, strengthening
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