8/8/2023 0 Comments Steel stackTherefore, the expansion of the weld nugget is reduced and achieving a sufficient nugget diameter d min is made more difficult. High heat dissipation occurs in the area of the faying surface (I) due to the thin outer sheet metal. Afterwards, the weld nugget expands over the entire cross section. During the welding process, the weld nugget in formed in the faying surface II due to the highest electrical resistance and the lowest heat dissipation. An asymmetric three-sheet stack-up made of two thick sheets and a thin outer sheet is shown in Figure 1. The requirements for a weld nugget, produced by resistance spot welding, are specified in. However, it should be noted that more complex components (sheet thickness ratio, different materials, and disparate surface conditions) react more sensitively to changing parameters. A sufficient joint quality is possible with a maximum sheet thickness ratio of 1:3. These stack-ups are made of different materials with disparate surface coatings and a high sheet thickness ratio, as shown in Figure 1. Resistance spot welding is made more difficult by the use of highly heterogeneous sheet stack-ups. Due to increasing demands of weight reduction, torsional stiffness and crash safety, three-sheet steel stack-ups for car body construction are required. Spot weld bonding is an established technique for the production of car bodies with a focus on a high degree of lightweight construction. This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( ), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The obtained results contribute to a direct verification of the welding process and an automatic detection of possible imperfect welds. In addition, the process of adhesive displacement during the squeeze time and the initial welding current are discussed on the basis of the electrical energy generated in the component to be welded. The corresponding characteristics of electrical resistance will be recorded by using an online measurement device. The individual three-sheet steel stack-ups used are made of low carbon steel (DX51), HSLA-steel (HX340) and UHS-steel (22MnB5). In this manuscript, different sheet stack-ups are examined with regard to their weldability lobes and their process behavior. These characteristics can be analyzed by using an online measurement device. During welding, a specific characteristic of the electrical resistance is created for each individual material combination. For an asymmetric sheet stack-up, the electrical resistance for every faying surface is highly differentiated. Depending on squeeze time and electrode force the adhesive will be displaced. The effective weldability lobe is reduced and an adjusted preheat current is necessary to reconstitute the weldability of a component. Adhesive applications lead to a change in process behavior of resistance spot welding. In order to achieve these individual requirements, the use of three-sheet steel stack-ups with adhesive applications for car body construction is one of the current strategies used in automobile manufacturing. In addition to increasing torsional stiffness and crash safety of the body, the aim is also to reduce the overall weight at the same time. The body of a typical compact car design has a weight share of approx. * e-mail: to the increased demands for reducing CO 2 emissions, improving fuel efficiency of modern vehicles has been continuously monitored. Sascha Brechelt 1 *, Philipp Neef 1, Henning Wiche 1 and Volker Wesling 1 ,2Ĭlausthal University of Technology, Clausthal Centre of Material Technology, Leibnizstraße 9, 38678 Clausthal-Zellerfeld, GermanyĬlausthal University of Technology, Institute of Welding and Machining, Agricolastraße 2, 38678 Clausthal-Zellerfeld, Germany
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