Research on process window diagrams of tube-compression by viscous pressure forming

Wrinkling is one of the major defects in tube-compression process. As a new method, the pressure distribution of viscous medium can be controlled when wrinkles occur in tube-compression process by viscous pressure forming (VPF) and then wrinkles can be eliminated under certain condition. So the tubecompression limit is greatly improved by expanding the deformation area in this new developed process. However, the limit of tube-compression by VPF is hard to be predicted according to existing forming limit theory. In this paper, process window diagrams considering some parameters of tube-compression length, tube-blank diameter, and limit diameter reduction were predicted by finite element method, and were verified by experiments. The results show that the diagrams can predict the limit diameter reduction of tube-blank, and also can reflect the states of wrinkles and the possibility of its elimination during tubecompression by VPF, which can provide guidance for the application of this forming technology.