Hybrid-Forging: Combined Forming and Joining of Sheet and Bulk Metal

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Lightweight structural components are often designed for the needs of assembly and function. They often have bulk- and sheet-elements. Nowadays, these elements are separately manufactured and subsequently joined in additional process steps, for example by welding or a screw connection.In the first funding period a simulative and experimental study of the basics of hybrid forging was investigated. Hybrid forging is the forging of bulk parts, the forming of sheet metal components and the joining of these parts in a single step. Material bonding mechanisms and positive locking have been evaluated in three model experiments (HS1 to HS3) using FE-simulations and practical experiments. The influence of the parameters deformation, temperatures of sheet metal and bulk elements, and the friction was investigated on the quality of the joint between solid and sheet metal element and the sheet thickness. In model experiment HS1 and HS2 partially a material bonding was achieved. In model experiment HS3 a positive locking was achieved. However, the sheets bulged partially, were bent unintentionally and were reduced in their thickness.The aim of the second period of this research project is the development of the hybrid forging based on the insights developed in the first period. The deformation of the sheet (bulging, bending, and sheet thickness reduction) shall be reduced and the quality of the joining shall be increased. The deformation is to be reduced by sheet materials with a higher strength and greater thickness, and by the use of blank holders. The joining quality is enhanced by a geometrically forced relative motion of the bulk in relation to the sheet metal element. An exemplary hybrid forging part with variable elements made of common sheet metal and forging materials as well as the deformation process will be developed. Furthermore, this example part should illustrate the different manufacturing operations, forming of sheet metal and bulk elements and joining (positive locking and material bonding) of the elements and allow a study of the interaction of forming and joining operations. Furthermore, forming tools are designed for experimental tests and metallurgical and mechanical properties of the hybrid parts are investigated, especially the joining areas.With the insight gained in this research the possibilities of designing structural components are extended that lightly loaded regions of a component can be substituted by sheet metal elements or elements can partially be reinforced by bulk elements. Due to the simultaneous bulk and sheet metal forming including joining the process chain is shortened compared to conventional process chains.