Abstract
Recently, friction stir (FS) welds are applied to aluminum alloy carbody structures of Shinkansen and commuter trains. Although FS welds are characterized by the property of suppressing mechanical strength degradation, it is important to identify their characteristics when evaluating the strength of carbody structures. FS welds generally consist of three zones: stir zone (SZ), thermo-mechanically-affected-zone (TMAZ), and heat affected zone (HAZ). Therefore, the hardness profile of FS welds is inhomogeneous. In this study, in order to identify the inhomogeneous mechanical strength of FS welds, we conduct the vickers hardness test and quasi-static tensile test using test specimens including FS welds. The test specimens are taken from the side structure of an aluminum alloy car. We apply the digital image correlation method for identifying local stress-strain curves in the quasi-static tensile test. Furthermore, we carried out a FE simulation under the same condition as the experimental test. FE model can express inhomogeneous mechanical properties. The simulation result was in good agreement with the experimental one in terms of stress-strain curve and fracture position.
