Characterization of a magnetorheological fluid with respect to its suitability for hydroforming

Nowadays the global warming and the shortage of resources represent big challenges. To cope with these deviances it is the duty of the automotive industry, to build up light weight constructions for high efficient vehicles. For example forming parts as components of exhaust systems or chassis components could be realized by hydroforming, a new flexible technology, which enables the realisation of undercuts and increases the forming limits. Thereby comparatively complex part geometries can be produced. Using this process the blank is deformed by gases or fluids as pressure media. In this case a magnetorheological fluid could be used. The key property of magnetorheological media is an increasing viscosity under magnetic fields. Thus they can not only serve as a pressure medium, but also act as a sealing in the flange area to prevent leakage. For a better understanding of the process a basic characterisation has to be done. Therefore an experimental setup is built up. Different parameters like feed rate and magnetic flux density are varied to get information about the behaviour of the tested fluid. The achievable cavity pressure is perhaps the most important parameter, because it determines the geometry of the part at the end of the forming step, especially at the small radii of the component. Another result of these tests is the fundamental potential of magnetorheological fluids for the process of hydroforming of blanks.