Optimal load path input in tube hydroforming machines

Tube hydroforming (THF) is a metal-forming process in which a tube is plastically deformed to conform to the die cavity by injecting a pressurized fluid inside the tube. To ensure that enough material is supplied to the die cavity, the tube ends are usually pushed towards the die cavity to feed the material. To successfully hydroform a part, good coordination between fluid pressure and material feed is necessary. This pressure–material displacement relationship is known as a load path. The load path is specific to a part, and it is entered in a THF machine as pressure versus time and displacement versus time input variables. A methodology of decomposing the pressure–displacement loading path as a time variable to obtain pressure–time and displacement–time variants that are optimal for the THF machine system is presented. The THF experiments for double T-shaped parts are carried out to demonstrate that using different pressure–time and displacement–time variants can result in a significant increase in the maximum power required by the THF machine actuators.