Hydroforming of locally heat treated tubes

In tube hydroforming, the process chain can be very long as it may involve several pre-forming operations (e.g. bending, crushing, end forming, etc.) which are usually followed by an intermediate annealing stage. Conventional annealing is performed in batches and it is often perceived as a long, relatively expensive and non-environmentally friendly operation. For this reason, in this paper local intermediate heat treatment is proposed as a promising alternative solution, in order to reduce the throughput process time. The study has been carried out on a real tubular motorcycle part, by performing both experiments and numerical simulations, in order to verify whether local annealing can be an effective substitute of conventional global annealing. Several alternative ways of locally heat treating an Al6060 tube right before hydroforming have been investigated. The results demonstrate that a feasible solution can be found, with local heat treatment of relatively small portions of the tube.