Hydraulic bulging process with axial feedings and strain field of U-shaped metal bellows

Based on the traditional hydraulic bulging process, an improved hydraulic bulging process with axial feeding in the bulging process was proposed. The finite element simulation and experiment of bellows formed by the traditional and improved hydraulic bulging processes were conducted. The grid strain measurement system analysis results of strain and wall thickness distribution of the metal bellows, obtained from simulation and experiment, show that the maximum thinning rates of the wall thickness under the traditional and improved processes were 15% and 10%, respectively. And the wall thickness distribution of the metal bellows formed with improved process was more uniform. The strain values from the root to crown of the waveform increased gradually. However, the strain values were smaller than those of traditional process due to the axial feeding of the improved process in bulging process.