Abstract: The hydroforming process for automobile lower arm is analyzed by a HydroFORM-3D FEM program，which is developed on the basis of a rigid-plastic model. The effects of forming process parameters such as internal hydraulic pressure，axial feeding，and friction conditions on the lower arm forming limit are performed and discussed. The numerical result is verified by actual experimental data. The comparison shows that the numerical analysis successfully provides the manufacturing information for the lower arm hydroforming，and it can predict the geometrical deformation and distribution of the thickness successfully.

Key words: FEM, Hydroforming process, Lower arm