An approach to process limitations in hydroforming of X-joints as based on formability evaluation

Experimental results of copper X-joint hydroforming have been compared with the results of FEA simulations. An influence of loading history and properties of deformed tubular material on process feasibility has been presented. The method of forming limit curve (FLC) prediction was utilised in order to determine the onset of strain localization and bursting failure. Prediction of failure based on the FLC commonly used for sheet metal forming has given a considerable underestimation of hydroforming limit for X-joints. Hence, the modified FLCm has been suggested that could be used in hydroforming process planning.