Numerical and Experimental Study of Tube Hydroforming for Aerospace Applications

In the tube hydroforming (THF) process, a pressurized fluid is used to expand a thin walled tube inside a closed die in order to fill the die cavity. THF has many advantages that render this process interesting for different industries such as automotive and aerospace. In this work, to investigate the effect of different process parameters, such as the friction condition, tube thickness and end-feeding on the final product, THF experiments were performed on stainless steel 321 (SS 321) tubes using a round-to-square die. Experimental loading paths were obtained via the data acquisition system of the hydroforming press, which is fully instrumented. An automated deformation measurement system, Argus®, was used to measure the strains on the hydroformed tubes. The THF process was simulated using Ls-Dyna software. The variation in the strain and thickness measured from the experiments were compared to the simulation results at critical sections. Comparison of the results from the finite element (FE) simulations and experiments showed good agreement, indicating that the approach can be used for predicting the final shape and thickness variations of the hydroformed parts for more complex shapes in aerospace applications.