Influence of spot welding in adhesive bonded steel sheets on formability and springback

Abstract

The adhesive bonded steel sheets have main application in the automobile and aircraft manufacturing sectors especially in body-in-white (BIW) applications. Most of the parts in these applications are formed structures. From the literature, it was found that the formability of adhesive bonded sheets is influenced significantly by adhesive properties and interface bonding. Early failure of interface bonding and delamination during deformation of adhesive bonded sheets are major issues that affect the formability. In the present work, the influence of spot welding in adhesive bonded steel sheets on formability issue is investigated. During spot welding of adhesive bonded sheets, location, size and number of weldments were varied at different levels. The weld sizes were in the order of Ø3 mm, Ø5 mm and Ø7 mm. In order to vary the location of weldment, the weld was spotted at 15 mm and 30 mm from the center of gauge region. The number of weld spot was varied like 1, 2 and 3. While varying location and number of weld spots, a constant weld size of Ø7 mm was maintained. Tensile test and V-bending process were carried out. The results like failure pattern, tensile behavior, and elongation were monitored in tensile test. Springback and delamination behavior were evaluated from V-bending process. The results show that there is not much difference in varying size of the weld spots. About 6% increase in elongation is observed with two weld spots at both the extremes of gauge region of the bonded sheets as compared with a single weld at the center. It is understood that deformability of bonded sheets region between two welds increases. In the case of weld location, the weld spot offset at 15 mm shows better elongation than the weld at center and offset at 30 mm. From the results, spotting weld at an appropriate location slightly away from the gauge region improves the elongation of bonded steel sheets, a reduction in springback and eliminated delamination are observed with spot welding of adhesive bonded steel sheets and concludes that the spot welds in the adhesive bonded steel sheets arrest the relative motion between two base materials, and influences the overall formability. The results of the present study could be useful in controlling early failure, formability, springback and delamination of adhesive bonded steel sheets.