the shear zone were calculated and converted to effective strains. Together with effective stresses obtained from shear stress measurements, the measured effective stress-effective strain curves of all three types of weld nuggets and their HAZ are shown in Figs. 8–10. Also shown in Figs. 8–10 are the corresponding true stresstrue strain tensile curves of the base metals. Figures 8–10 illustrate that the tensile strength of all three weld nuggets (triangular data) are higher than the base metal substrate shown by the solid line. Figure 8 shows data for the Aural 2-T7 to Aural-2-T7 alloy combination, where no change in alloying occurs between the two welded sheets. In this case, the nugget still shows sig- WELDING RESEARCH A B A C D B Fig. 7 — Shear strain maps at maximum load for the heataffected zone in “aswelded samples”: A — Aural2T7 to Aural2T7 spot weld; B — Aural side in an Aural2T7 to AA5754O spot weld; C — Aural2T7 side in an Aural2T7 to AA6022T4 spot weld; D — AA6022T4 side in an Aural2T7 to AA6022T4 spot weld. Table 3 — Resistance Spot Welding Schedules(a) Spot Weld Force, kN Preheat Preheat Cool Weld Weld rms(b) Time, ms Current, kA Time, ms Time, ms Current, kA Aural2T7 4.9 30 ~10.0 10 156 33.3 + AA5754O Aural2T7 5.3 30 ~10.0 10 156 32.5 + AA6022T4 Aural2T7 6.7 50 ~6.0 10 267 27.0 + Aural2T7 (welding schedule 1) Aural2T7 + Aural2T7 5.8 50 ~10.0 10 247 29.5 (welding schedule 2) (a) No post heat was used for any of the weld schedules. (b) Pulsating DC current was used during the welding step and is given as rms current. 252-s WELDING JOURNAL / JULY 2016, VOL. 95 C Fig. 6 — Shear strain maps at maximum load for weld nuggets in “aswelded samples”.: A — Aural2T7 to Aural2 for welding schedule 1; B — Aural2T7 to AA5754; C — Aural2T7 to AA6022.
Welding Journal | July 2016
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