Effect of Friction on Corner Filling Deformation in Tube Hydroforming Process by Real-Time Measurement

Tube hydroforming is an advanced technology for manufacturing thin-walled tubular components with irregular cross-sections. However, a real-time measurement and quantitative research on the friction effect in hydroforming process has never been involved. In this paper, the unloading theoretical condition for tube blank after contacting with die during corner filling process was derived based on ideal rigid plastic assumption. It is predicted that the tube blank would unload quickly once it contacts with the die due to friction. Furthermore, an experimental setup was firstly developed for visual measurement of corner filling deformation in tube hydroforming process. Based on 3D full-field strain measurement technology (3D-DIC), this setup can be used to realize a real-time measurement of strain field on the tube blank during corner filling process. Then the effects of friction and tube properties on deformation behavior were investigated by pure lead (approximately ideal plastic model) and aluminum alloy (hardening model). It is shown that the friction causes pure lead tube blank to unload after a very small deformation of less than 0.02 in contact with the die, which basically verifies theoretical analysis results. For aluminum alloy tube blank with strong hardening ability, it continues to deform after sticking on the die surface. There is little effect on improving the uniform deformation of pure lead tube by reducing friction with lubricants, but it is very effective to improve the uniform deformation of aluminum alloy tube.