| The emerging of the TWB (Tailored welded blank) technology has brought a revolutionary reform to the design and manufacture of vehicle body. It has broken through the traditional idea that all parts of the vehicle body are made of the same kind of blank. Spot welding tailored blank, one kind of tailored welded blank, is comprised of metal sheets with various specification, material and dimension that are welded by splicing method or joining method. And the stamping parts that have been optimized in shape, strength and weight can be acquired via the blank stamped consequently. Compared with other kinds of TWBs, the application of spot welding tailored blank has many advantages such as high efficiency and low cost, etc. In this paper, the spot welding tailored blank, made of general vehicle body sheets, is the research subject. The forming capability of spot welding tailored blank is systematically studied by integrating test method and theoretical analysis in harmony and compared with numerical simulation result. The main fruits and new ideas are as following:1. The testing results indicates: (1) During the shaping of spot welding tailored blank, the distortion is mainly contributed by the base metal. The distortion of welding spots is comparatively lesser. The nugget of the welding spots is hard to distort especially. (2) The spot welding tailored blank shows compatibility of formability generally. Only the local distortion of the blank is affected by welding spots. The forming of the whole blank is rarely influenced by them. (3) The total elongation of spot welding tailored blank is below the total elongation of the base metal. But during the smooth tensile stage before tensile buckling, the elongation of the blank is correspond to the base metal.2. The distribution of stress around the welding spot is obtained by adopting stress function. The stress, which can make the plastically deforming area appear around the welding spot, is determined on the base of Swift-Hill yield criterion. The strains of spots on the tensile axis are acquired by use of single curve assumption. The comparison between the theoretical result and numerical simulation result indicates the theoretical calculation method is only applied to small elastic-plasticity deformation.3. The mechanical property parameters of bi-layer -plate at elastic stage and plastic stage are acquired by theoretical analysis, then the theoretical forming limited diagram of bi-layer plate is plotted. Pointing at the characteristic of spot welding tailored blank, the conception of probabilistic forming limited diagram (P-FLD) is presented. Combined with component forming limit diagram, material selection can be made initially and the safety margin in production can be determined. |
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