Finite Element Analysis Comparing the Formability of Large Hollow Protrusions in Tube Hydroforming

The fabrication of large hollow protrusions for various types of metal joints using conventional stamping, welding, and casting methods often results in non-uniform deformation, material thinning, residual stresses, and thermal stresses. These issues compromise material continuity, reduce structural stiffness, and diminish overall strength. To address these challenges, the present study employs Tube Hydroforming (THF) technology to optimize the process of forming large hollow protrusions in T-shaped and X-shaped copper joints. The process was simulated using the Finite Element Method (FEM) in Abaqus/CAE 3DEXPERIENCE R2019, incorporating a plastic material model and nonlinear contact conditions to analyze and compare five critical parameters: the effective range of forming fluid pressure, the distribution of forming stress within the component, the components of plastic deformation, the wall thickness distribution, and the height of the large hollow protrusion. The results indicate that both joint types share the same effective forming fluid pressure range (Pi - max = 23 MPa + 30 MPa), and the achieved height of a single protrusion is equivalent (U1T(23 MPa) = 21.96 mm → U1T(25 MPa) = 22.82 mm → U1T(30 MPa) = 24.89 mm; U1X(23 MPa) = 21.31 mm → U1X(25MPa) = 22.22 mm → U1X(30MPa) = 24.82 mm). Furthermore, the wall thinning at the apex of the large hollow protrusion was found to remain within acceptable limits for both components (thinning ratio: emin-T = -24.17%, emin-X = -10.83%), while the transition zone of the X-joint exhibited more intense thinning; yet remained within safe margins. This research provides a reliable three-dimensional simulation framework for optimizing the THF process, reducing experimental costs, and improving product quality in the manufacture of large hollow protrusions for various types of hollow joints.