The article reports the results of an experimental and theoretical study of a single-stage cold forging process. This process was used to produce hollow balls with an outside diameter of 30 mm, with two central openings. The forgings were made from tubular aluminum alloy billets with wall thicknesses of 3 mm and 4 mm. The other dimensions of the billets (outer diameter and height) were varied, always making sure that the volume of the forging remained constant. The results of the study were discussed with a special focus on forming conditions, quality of the forging, potential limitations of the process, and the impact of billet dimensions (also expressed as non-dimensional slenderness ratios) on the conditions of the forming process.
The paper presents the results of a numerical analysis (by FEM) of a new forging process for producing a hollow ball with an outside diameter of 30 mm and a wall thickness of 4.4 mm. It was assumed that the ball forging would be cold formed from hollow billet (tube) made of 19MnCr5 steel. The effect of billet dimensions (diameter, height and wall thickness) on the forming process was investigated, which led to identification of basic shape defects and determination of the billet dimensions required for producing balls of the desired geometry. The ball forming conditions, including force parameters of the process, are thoroughly investigated.
This paper investigates a cold forging process for producing hollow balls made of an aluminium alloy. The forging with an outside diameter of 30 mm is formed from a tube section with a 2-mm wall thickness. Preliminary tests have shown that in traditional die forging, the use of a billet with such a small relative thickness not only limits the range of applicable geometric parameters but also causes buckling. The authors propose to solve this problem by using an additional tool that has an active effect on the inner surface of the workpiece, and thus makes it possible to control the forging process conditions. The tool is a plastic insert, i.e., an additional flexible core made of a low-melting alloy. Theoretical and experimental results presented in this paper provide a considerable insight into the cold forging process for thin-walled hollow balls. The effects of the plastic insert geometry and dimensions on the forging process are also examined. A solution is proposed to ensure that the forged part meets all requirements.
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