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Hot stamping patchwork blanks technology can flexibly adjust the mechanical properties by designing different thicknesses and profiles of the main blank and the patched blank. Due to the spot welding connection between the main blank and the patched blank, the material flow between them is uneven and crack defects easily occur. To investigate the i...
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During the hot stamping process, heat exchange always occurs between the hot sheet and cold tools. The interfacial heat transfer in the whole-forming process will not only affects the forming quality of the parts but also partially determines their post-form mechanical properties and microstructure distribution. As an essential parameter, the inter...
Citations
... Since the main blank and the patchwork blank are connected before hot-stamping forming, the number of required dies can be reduced. This method has been widely used in automobile A-pillar, B-pillar, and front reinforcement beams, among others [11][12][13]. Its advantages are a good collision safety, high bending load, local reinforcement, and good lightweight effects. ...
With increasingly severe environmental problems, energy saving and environmental protection have become two important issues to be solved in the automobile industry. Patchwork blank hot-stamping technology can be used to obtain light-weight and high-strength parts and is thus increasingly used in the manufacture of autobody parts. Because the main blank and the patched blank need to be connected through spot welding before forming, the welding spots’ arrangement has a great influence on the formability of the part. In this study, a thermal–mechanical coupling finite element analysis model of A-pillar patchwork blanks was established. With the thickness of the patched blank, the distance between the welding spot and the external contour of the patched blank, and the number of welding spots as optimization variables, together with the maximum thinning rate and the maximum welding spot force as objectives, the influence of welding spot arrangement on forming quality was analyzed, and the welding spots’ arrangement was optimized using a central composite design (CCD), the response surface method (RSM), and the genetic algorithm (GA). The results showed that when the initial welding spot was located close to the contour of the patched blank, the bending moment was greater when the weld spot passed through the die corner, leading to the rupture of the welding spot or its surrounding base material due to the greater thinning rate. When the patched blank was thicker than the main blank, the main blank cracked during the forming process due to a greater increase in the thinning rate. The optimal solution of the weld spot arrangement on the A-pillar patchwork blanks was a 1.2 mm thick main blank, 0.8 mm thick patched blank, a distance of 29 mm between the weld spot and the contour line of the patched blank, and 16 weld spots. Hot-stamping experiments were conducted using the optimized weld spots’ arrangement, and high-quality parts were obtained.
... Energy consumption and environmental pollution promote the development of automotive lightweight [1][2][3]. In order to reduce automobile weight, a great number of lightweight materials such as aluminum alloys are applied to the automobile body [4][5][6][7]. However, with the application of aluminum alloy also brings difficulties in joining. ...
In recent years, the flat-clinching process was gradually attracting attention due to the widespread application prospects in joining lightweight materials. However, the unsightly joint bulge may limit the use of the flat-clinching process. In this article, a novel reshaping process was proposed to overcome the shortcomings of flat-clinching joints. Reshaping flat-clinching joints in material AL5052 was produced by different reshaping forces. Meanwhile, the forming mechanism and material flow of the reshaping process were studied experimentally. The influence of different reshaping forces on the mechanical properties and geometric parameters of the joint was illustrated. The study results show that the reshaping process not only reduces the bulge height but also improves the mechanical properties of the joint. The reshaping process increases the neck thickness and interlocking value of the joint, leading to enhanced tensile and shear loads. This tendency becomes greater as the reshaping force increases. The flat-clinching joint with 40 kN reshaping force exhibits the highest mechanical properties, enhancing the shear load by 24.2% and the tensile load by 8.6% compared to the joint without the reshaping process.
