WELDING RESEARCH A B C DECEMBER 2016 / WELDING JOURNAL 487-s 3 = (10) θ θ ID PO where HPO is the hardness of pullout failure location, and HIF is the hardness of interfacial failure location. Apply Equation 10 to the Types I and II joints of the 1.0/1.0/1.0 mm stack, The failure location in the PO mode was the BM. The average hardness of the BM was 95 Hv. In the case of Types I and II joints, the failure location of the IF mode was the failure location in the interior of the LCGZ, where the porosity is hard to form. Thus, the Aporosity equals 0 and P is 1. The average indentation was about 70% of the original sheet thickness, i.e., tID was 0.7 mm. The rotation angle was measured after the tensile-shear test. It was nearly zero when the joint failed in the IF mode (16 kA, 200 ms), while it was 2 deg when the joint failed in the PO mode (20 kA, 200 ms). The critical nugget diameter for Types I and II joints can be obtained as follows: It can be seen that the predicted value is very close to the experimental result of 5.9 mm. In the case of a Type III joint, the failure location in the IF mode was still in the interior of LCGZ or along the interface between the LCGZ and SCGZ. A B C D Note that the failure location in the PO mode changed to PMZ, as shown in Fig. 9. The average indentation was about 90% of the original sheet thickness, i.e., tID was 0.9 mm. The average rotation angle was about 2 deg when the joint failed in the IF mode (16 kA, 200 ms), while it was 7 deg when the joint failed in the PO mode (18 kA, 200 ms). Thus, the critical nugget diameter for the Type III joint can be obtained as follows: The result is a little larger than the experimental value (5.1 mm). Equations 1–11 are not suitable for the Type IV joint because the failure mode of the Type IV joint is different from the other types of joints. This pa- (DC )Types I&II = 3tID Pf HBM HLCGZ cos��IF cos��PO = 3��0.7 0.6 95 55 1 cos2 deg ��6.0 mm (11A) D t Pf H H cos C cos IF IF PO (DC )Type III = 3tID Pf HPMZ HLCGZ cos��IF cos��PO = 3��0.9 0.6 65 55 cos2deg cos7deg ��5.3 mm (11B) Fig. 15 — Effect of button size on the peak load of the Types I, II, and III joints for the 1.5/1.0/2.0 mm stack. Fig. 16 — Stress analysis in the weld area: A — Weld rotation; B — IF failure; C — PO failure (Ref. 23). Fig. 17 — Schematic of joint rotation in the 1.0/1.0/1.0 mm stack: A — Type I joint; B — Type II joint; C— Type III joint; D — Type IV joint.
Welding Journal | December 2016
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