Although FSW is an effective joining method which controls distortion, there is a problem in joining thick plates as gap opening of joining line (hereafter called rotation distortion) arises which makes the operation impossible. The same behaviour is observed when FSW is applied to butt joint welding of thin aluminium sheets. As it is expected that FSW substitutes traditionally arc welding, for example in automotive industry, an effective method to avoid rotational distortion is necessary. The authors of the present study assume that the rotational distortion is generated by heat expansion in the heating region near the FSW tool and, therefore propose a method to control the rotational distortion using thermal processing, which means heating in a position parallel to the welding line. The validity was clarified by using numerical welding simulation. In order to verify the FSW rotational distortion control method by heating, a FSW demonstration was carried out. TIG torches were used to heat control, which were fixed on the FSW drive with the support jigs and moved with the FSW tool. Thermocouples and a clip gauge were attached to the specimen. The hollow test piece made of thin aluminum sheets were butt welded. In order to obtain the TIG conditions equivalent to the heat input by FSW, the preliminary test was performed, and the torch height and an electric current were decided. The rotational distortion control method by heating was demonstrated by confirmation tests and thought to be very economical. It was found that a numerical simulation was applicable to the rotational distortion prediction of FSW.
Control of rotational distortion in friction stir welding
2004
7 Seiten, 7 Bilder, 1 Tabelle, 2 Quellen
Aufsatz (Konferenz)
Englisch
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