Modelling of micro tubes hydroforming processes

The wall thickness of formed micro tubes is not uniformly distributed and is difficult to control. The macro mechanics FE modelling can not be used to simulate such effects in micro tubes hydroforming processes. In this paper, a simplified plain strain Crystal Plasticity Finite Element (CPFE) based modelling technique has been developed and used to capture the localized thinning and failure features for hydroforming of micro tubes. Grains within the tube workpiece, their distributions and orientations are generated automatically using the developed VGRAIN system. A set of crystal viscoplasticity model is implemented in ABAQUS/Explicit FE code through the user-defined subroutine, VUMAT. Several cases have been studied and the localised thinning has been analysed for different microstructures of the material using the CPFE modelling technique, and the method is verified by the test result.