| dc.description.abstract | Tungsten inert gas welding and vacuum brazing butt joints and T-joints of Al–Mg–Si alloy 6061 in the artificially aged condition T6 were studied. Microhardness, tensile, constant amplitude and variable amplitude fatigue loading tests were performed. The experimental S-N curves were compared with the fatigue design curves recommended by the International Institute of Welding, British Standard, and Eurocode 9. Two mean stress correction methods, Goodman and Gerber, were evaluated.
For the tungsten inert gas welding joints, the area with the lowest microhardness was the HAZ. For the vacuum brazing specimen, no clear HAZ was observed. Because the weldment was heated to a uniform temperature in a vacuum, so local overheating did not occur.
In terms of the tensile properties of butt joints, the tensile strength of the vacuum brazing specimen increased with specimen thickness, whereas that of the tungsten inert gas welding welding specimen decreased.
Tungsten inert gas welding butt joints and T-joints of AA 6061-T6 achieved higher fatigue strength as compared to the fatigue design curves of IIW, BS 8118, and Eurocode 9. In the lower life region (N = 104 ~ 105), it was found that the fatigue strength of vacuum brazing butt joints was lower than that of IIW FAT 45, but still higher than those of the BS 8118 class 42 and Eurocode 9 category 56-7.
When tungsten inert gas welding or vacuum brazing joints of aluminum 6061-T6 was subjected to a variable amplitude loading with tensile mean stress, Goodman method was suitable to modify the mean stress effect. For T-joints, the fatigue life of the tungsten inert gas welding specimens given the bracket history can be predicted using the S-N method. The fatigue life of the vacuum brazing specimens under the bracket history can be predicted using the Goodman mean stress correction method.
In terms of the size effect on the fatigue life, the thickness correction method recommended by the IIW was applicable to the tungsten inert gas welding joints of aluminum 6061-T6. This article proposed an innovational thickness correction method based on the ratio of the ultimate tensile strengths of specimens with different thickness. For butt joints of vacuum brazing, the tensile strength–based thickness correction method was better than the thickness correction methods recommended by the International Institute of Welding. For T-joints, vacuum brazing is required to carry out thickness correction in the higher life region. | en_US |