Papers by Keyword: Sheet Metal Hydroforming

Abstract: Sheet metal hydroforming has gained increasing interest during last years, especially as application in the manufacturing of some components for: automotive, aerospace and electrical appliances for niche productions. Different studies have been also done to determine the optimal forming parameters making an extensive use of FEA. In the hydroforming process a blank sheet metal is formed through the action of a fluid and a punch. It forces the sheet into a die, which contains a compressed fluid. Many studies have been focused on the analysis of process and geometric parameters influence about the hydroforming process of a single product with main dimensions till to 100 mm. In this paper the authors describe the results of an experimental activity developed on two different large sized products obtained through sheet metal hydroforming. Different geometric and process parameters have been taken into account during the testing phase to study, in particular, the punch radius influence on the process feasibility. An ANOVA analysis has been implemented to study the influence of geometrical and process parameters on the maximum hydroforming depth. Through this work it has been possible to verify that in the hydroforming process of large size products geometry and, in particular, punch radius, are some of the main factors that influences the feasibility of the products. Different considerations can be made about the effects of the blankholder force and the fluid pressure on the maximum hydroforming depth. As further developments, the authors would perform a numerical study in order to enlarge the knowledge of the process design space to other possible values of the punch radius.

Abstract: This paper presents a sectionwise hydroforming technique for manufacturing of large-area multi-cell sheet metal structures in terms of hump plates. The sectionwise hydroforming technique allows production of hump sheets with variable width and length. The hump plates are based on hexagonal hump geometry. The hump height is optimized for the application as a partition wall in light utility vehicles. Manufactured hump sheets feature a high contour accuracy which allows joining of two hump sheets to a large-area hump plate (up to 1,800 x 2,000 mm). The hump plates have been successfully tested in a load test which proves their potential for light utility vehicles.

Abstract: In this paper, the use of partially or tailored cladded blanks is proposed for the production of multifunctional lightweight components. Therefore, the non-joined sheet areas will be formed to hollow structures by hydroforming subsequent to the partial cladding operation. The paper presents results of research work on the production processes and potential applications of partially cladded blanks in the field of thermal engineering and automotive engineering. Furthermore, it is focused on possible developments regarding the use of multiple materials and process combinations for sophisticated applications e.g. in the field of lightweight constructions.

Abstract: The further development of innovative forming processes like sheet metal hydroforming is only possible with the help of detailed knowledge about the workpiece properties and their formation depending on the process strategy. Up to now, the knowledge about the formation of macroscopic residual stresses in high-pressure sheet metal forming (HBU), regarding the influence of the sheet material properties, is still insufficient. The characteristics of the specific forming procedure HBU lead to specific stress and strain gradients in the sheet cross-section, and therefore lead to a characteristic distribution of the induced macroscopic residual stresses, particularly in the workpiece bottom zone. This paper decribes the investigations on the influence of the sheet material flow curve on the macroscopic residual stress distribution in the workpiece bottom.

Abstract: A promising approach to control the material flow within deep drawing and workingmedia based forming processes is the structuring of the tool surfaces in the contact zones between workpiece and die. In order to obtain a sufficient and an optimised material flow respectively – especially for non-symmetric or non-uniform workpiece geometries – a locally adapted distribution of surface structures is a practicable solution. The macroscopic, and also the microscopic surface structures can be manufactured sufficiently by means of a high-speed cutting process. The shape of the tool surface structure has a significant influence on the tribological conditions between workpiece and die. To adjust the surface structure distribution to the required material flow distribution, detailed knowledge about the correlation of the material flow from the tribological conditions between sheet and the forming tool is required. A further innovative approach, particularly for decreasing the friction coefficient, is the use of an innovative hydrostatic pressure system using fluid ducts. Its functional principle is based on the reduction of the contact shear stress at the sheet surface in the contact zone with the forming tool by means of locally applying a hydrostatic fluid pressure. To obtain information about the correlation of the material flow from the tool surface structures and from the parameters of the hydrostatic pressure system respectively, fundamental investigations have been carried out. In order to optimise the material flow, these toolbased approaches can be used as stand-alone solution, or in addition to other systems. If the surface structures and a hydrostatic pressure system are used in combination with the multi-point blank holder, which has already been qualified for the high-pressure sheet metal forming (HBU), a powerful system for the material flow control is available.