A B Fig. 1 — Magnetic pulse welding of tubular workpieces. A — Setup; B — process principle; and C — image of the weld seam (Ref. 6). A B Fig. 2 — A — Onesided welding; and B — twosided welding. Adapted from Ref. 7. A B Fig. 3 — A — Schematic showing working lengths; B — marks for visioplastic analysis of the flyer deformation; and C — picture of the experimental setup. ing length,” lw — Fig. 2). It has been reported by sources such as Zhang (Ref. 7) that the determination of a one- or two-front welding process can be done using the axial positioning of the workpiece in a coil of maximum working length lcoil. If lw < lcoil, the process will occur along a single front where the front edge of the flyer makes impact with the parent and proceeds via a single front onto the parent — Fig. 2A. If lw ≥ lcoil, a twofront process occurs where the flyer impacts the parent in the center of the field shaper/coil width and continues outwardly along two fronts — Fig. 2B. Experiments based on two-front processes have been performed by Kojima et al. (Ref. 8). The purpose of this work was an evaluation of the tapering angle of the base part on the length of resulting welds. Two-front welding processes between aluminum alloys and SPCC steel sheet joints were performed by Aizawa et al. (Ref. 9) using a flat coil with a maximum working length lcoil = 5 mm (0.2 in.). Faes et al. (Ref. 10) reported that the overlap of the field shaper edge and outer workpiece had a significant effect on (tube) welding conditions for copper/brass joints. Working distances of up to 5.5 mm (0.22 in.) were evaluated on a field shaper with a maximum working zone lcoil of 15 mm (0.59 in.). No experiments were performed with two-sided fronts, and results beyond the formation of a weld were not evaluated. There are distinctive reasons that a one- or two-front welding process may be more beneficial for a given application. However, these have remained largely neglected in literature pertaining to MPW. Zhang (Ref. 7) noted that for a one-sided front, less charging energy was required for a given increment of axial tube deformation. A transition zone between one- and two-fronted processes may exist, for instance with working lengths close to but not exceeding the coil length; however, evaluation of this has not been found in literature. There is also a lack of publications discussing an experimental comparison of one- vs. twofront welding, and no works with indepth analysis and comparison of the front regimes. The purpose of this work is to evaluate the effect of the working length on the features of MPW joints and is an expansion of first results presented in Ref. 11. Here, the general phenomenon of the influence of the axial workpiece positioning on front formation was revealed. This was done by basic experiments and numerical analysis. Experimental and Numerical Methods Joining Materials and Tools Flyer materials consisted of EN WELDING RESEARCH Table 1 — Aluminum EN AW6060 Alloy Composition (by wt%) (Ref. 12) Mg Mn Fe Si Cu Zn Cr Ti Other Elements EN 0.35–0.6 0.1 0.1–0.3 0.3–0.6 0.1 0.15 0.05 0.1 ≤0.05 AW6060 102-s WELDING JOURNAL / MARCH 2016, VOL. 95 C C
Welding Journal | March 2016
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