Fabrication of automotive titanium bipolar plates by uniform pressure electromagnetic incremental forming based on arc spiral coil

Abstract Facing the forming requirements of large-sized automotive titanium bipolar plates (BPPs), a uniform pressure electromagnetic incremental forming (UP-EMIF) process was utilized. Corresponding simulation and analysis were conducted based on the designed arc spiral coil. Analysis of the magnetic field revealed that during the forming process, electromagnetic forces on the coil wire tended to compress in radial direction, while the electromagnetic forces on the outer channel exhibited repulsive tendencies toward the driver sheet, and the electromagnetic forces on the driver sheet transitioned from a wavy pattern to a uniform distribution. Velocity and equivalent strain analysis showed that the maximum deformation velocity of the blank occurred at the bottom of the channel, reaching 195m/s. The highest equivalent strain of the blank occurred in the rounded corner R region, which was prone to thinning of wall thickness. Based on these findings, UP-EMIF and traditional quasi-static drive rubber pad forming (QS-DRPF) experimental devices were developed, and a comparative study on the forming of 0.1mm thick automotive titanium BPPs was conducted. Research indicated that successful production of a titanium BPP measuring 485mm×195mm was achieved using three consecutive discharges of 9kV in each discharge region under the discharge capacitor of 100μF, an acceleration distance of 2mm, a coil overlap rate of 15%, and a 0.3mm thick Cu110 driver sheet. The depth of the channels was 0.4mm (channel depth-to-width ratio of 0.53). Compared to traditional QS-DRPF, the 9kV UP-EMIF reduced channel thinning effectively, with a maximum thinning rate of 18.2%, while simultaneously improving channel filling, with a maximum filling rate of 96.3%. This demonstrates the feasibility of UP-EMIF as a process for fabricating automotive titanium BPPs.