Metal Foam Filled Hydroformed Tubes: Production and FEM Simulation

The marriage of the Tube HydroForming (THF) process with metal foams is interesting for different reasons: a) THF parts are naturally suited as cases to be filled by an internal metallic foam reinforcement and therefore for structural applications; b) the possibility to increase the mechanical strength of hydroformed parts allows to plan the THF process more freely and flexibly. These components, made of an outer hollow thin compact metal skin and a cellular lightweight core may find several applications in different industrial fields. In order to allow for an efficient and effective product/process design with a concurrent engineering approach, the structural performance of these composite parts must be predicted by means of FEM calculation. The optimal combination of tube and metal foam properties must be found. While FEM simulation of bending and hydroforming is state of the art, the accurate FEM simulation of the mechanical behavior of metal foams cannot be considered fully established. In the first part of this paper the foam-filling production cycle of a simple hydroformed aluminum part is shown, in order to discuss some of the design and manufacturing issues that can be faced in FEM based product/process analysis, concerning the thermal effects on the tube materials, the ability of completely filling the tube, the foam/tube interface conditions, the uniformity of cell distribution. A few potential applications of foam-filled hydroformed tubes are also presented. In the second part of the paper, the common methods and formulations for FEM simulation of foam based structures are discussed, and a new and very promising method is proposed.