Optimal Design of Stamping Process for Fabrication of Titanium Bipolar Plates Using the Integration of Finite Element and Response Surface Methods

Due to the high importance of metallic bipolar plates (BPPs) in proton exchange membrane fuel cell (PEMFC) from mechanical properties and ease of production points of view, titanium is selected because of its excellent corrosion resistance and low density. The present study deals with the forming of titanium ultra-thin sheet (with a thickness of 0.1 mm) as an alternative for BPPs using the stamping process. A finite element (FE) model is developed to simulate the process, and the effect of forming parameters and their optimal level are found via response surface methodology (RSM). In this design, clearance of die, stamping speed, and die/sheet friction coefficient are assumed to be as input variables and the formability of the titanium sheet in terms of maximum filling depth of the microchannel is investigated as output. A strain-based damage model is considered to examine the failure of the sheet during the simulation. The FE results demonstrate that the friction coefficient and clearance are the most remarkable parameters on the maximum filling depth with 50 and 46% of contributions, respectively. Changing the stamping speed has no tangible influence on the stampability of the titanium sheet. In addition, a regression model for estimating the maximum filling depth is represented based on the input variables. Eventually, a stamping die setup is fabricated and some experiments are carried out to validate the accuracy of the FE simulations and RSM results.