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In recent years the use of metallic bipolar plates for fuel cells is considered. Several studies have been conducted on the various methods of forming these plates. Most of this research has been done on the serpentine flow fields. While in some cases that the pressure drop is important factor, the pin-type flow fields shows good performance. In this research, hydroforming of metallic bipolar plates with circular pin-type pattern from stainless steel 304 with 0.11mm thickness is investigated experimentally and numerically. For this purpose, the effect of geometrical parameters such as the die wall angle, the die chamfer dimension, the depth-to-width ratio of the die, and forming pressure on the profiles, filling percent, thickness distribution and thinning percent of the formed parts are investigated. In this regard, two dies with wall angle of 0 and 15 degree were prepared. Then experimental tests were done at different pressures. After performing the required tests, the results show that the die wall angle leads to a more uniform thickness distribution and higher precision of the parts profile. Also the suitable range of die geometrical parameters was determined.

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Metal bipolar plates are key components in fuel cells that are considered as the best alternative to replace graphite plates. Material selection in bipolar plates depends on its weight and corrosion resistance. Metallic bipolar plate can be considered as the best alternative instead of graphite and composite plates. One of the new processes in order to produce this plat is gas blow forming process. In this study, forming of AA8111 bipolar plates with 200 µm thickness in concave groove dies is investigated by gas blow forming process at various pressures (20, 30 and40 bar) and temperatures (300 and 400 ° C). The filling percent of die at various wall angles and depth to width ratios are examined. According to the dimension of channels, maximum and minimum thinning percentage at high temperature and pressure are investigated. Results show that at wall angle of ∝=0, and the depth to width ratio of h/w=0.5, rupture occurs at pressure of 20bar and at temperature of 300° C and at pressures of 20 and 40 bar at temperature of 400° C. The best channel filling with lowest thinning obtained at ∝=15 and h/w=0.5.

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Metallic bipolar plate is one of the main parts of fuel cell. Several methods were used by researchers to manufacturing bipolar plate such as stamping, hydroforming and electromagnet forming. The effect of process parameters on dimensional accuracy of metallic bipolar plates in rubber pad forming process has been investigated in this study. ABAQUS/Standard finite element software is used to simulate the process. The accuracy of the results of simulation process is evaluated by using experimental results. To perform experimental procedures, rigid die with parallel flow field is used to form SS316 bipolar plate with 0.1 mm thick. For this purpose the effect of punch load, rubber hardness, rubber thickness and clearance between die and container on the dimensional accuracy of the formed parts is investigated. In this regard, rubber layer with hardness of 55, 70, 85 and 90 Shore A and thickness of 1.5mm up to 5.5mm were used. The result show difference between lateral and central channel depth, the amount of disparity will decrease by increasing in punch load, as a result the dimensional accuracy will increase. According to the result, increase in hardness and thickness of the rubber layer lead to improve the dimensional accuracy. Also considering clearance between die and container decrease the difference between lateral and central channel depth and eventually cause increasing in dimensional accuracy of formed part.

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In recent years, development of polymer electrolyte membrane fuel cells (PEMFCs) has been considered to generate electricity and heat. Among main components of PEMFCs, bipolar plates (BPPs) have significant influence on cost and performance of the system. Metallic BPPs, formed using thin sheets, have been developed as alternative to conventional graphite plates because of advantages such as suitable cost, mechanical strength and power density. Flexibility of the sheets and spring back during forming process make dimensional errors inevitable and lead to inappropriate contact pressure distribution between BPPs and gas diffusion layer (GDL), resulting in decrease of fuel cell performance. Excessive accuracy in BPP production leads to increase the final cost and decrease the general usability of the technology. Therefore, to reduce unnecessary costs, managing design process and improving efficiency, analysis of BPP dimensional errors is done using finite element method and Monte Carlo simulation (MCS). First, contact model of the metallic BPP and GDL is developed and heights of each channel and each rib of BPP are fully parameterized due to stochastic variations of dimensional errors with normal distribution. Then, contact pressure distributions of GDL (Pave, Pstd) for different dimensional errors are obtained by MCSs. Increasing dimensional tolerance from 0.015 mm to 0.075 mm, average contact pressure (Pave) has decreased by 11% and standard deviation of contact pressure (Pstd) has increased up to 90%. Namely desirable distribution of GDL pressure is reduced by increasing the dimensional error and suitable dimensional tolerances for BPPs can be determined according to engineering requirements.

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