| PEMFC is a device that can directly translate chemical energy in fuel and oxidant effectively into electric energy. PEM fuel cell is recognized by the U.S. Department of Energy (DOE) as the main candidate to replace the internal combustion engine in transportation applications for its excellent advantages such as: high energy consistency and low pollution, fast start up at the room temperature, no electrolyte leakage, water easily exchange, long life and high specific power, specific energy and so on. However, high cost is the main factor that to obstruct the PEMFC to be commercial used. Bipolar plate as the dominate component element of the PEMFC takes over a majority cost of the fuel cell about 30-45%. To reduce the cost of the PEMFC, the study of the metallic bipolar plate becomes a hot point in the PEMFC field for the metallic hold the excellent potential, e.g. high mechanical strength and excellent forming ability. Now, various methods and techniques have been developed to manufacture the metallic bipolar plate since it should be high dimension precision, high surface quality, produced in a large scale to reduce the cost and so on. A novel and feasible method to manufacture the metallic bipolar plate was presented in this paper.Rubber pad forming process was applied to manufacturing the metallic bipolar plate, and this study was mainly concentrated on the following points:Rubber pad forming is a process that adopts a rubber pad to acts as the upper die or the lower die. To obtain a larger forming force, the rubber pad should be contained in a container. Because the forming force of the rubber pad forming process is usually larger than that of the traditionally stamping process, the designation of the container is very essential before the process design stage. The mathematical relationship between the interior size and the ex-radius of the container was obtained by building mechanical model of the container at the working state, performing the finite element (FE) analysis and optimizing the fillet radius of the container at the corner.3D FE simulation of the rubber pad forming process was performed to analyze the effect of the process parameters on the forming process. The 3D FE model was evaluated by comparing the result of the experiment, and it is proven that the model was valid. Based on the valid model, the effect law of the outer radius, draft angle and punch velocity on the forming process was obtained. Meanwhile, the forming limit diagram (FLD) and the thickness variation of the formed part was analyzed by this model.According to the bipolar plate sample, the equipment of rubber pad forming was designed and manufactured, and the rubber pad forming experiment was conduced. The effect of the rubber pad hardness and the material property of the stainless steel on the forming process were analyzed by the experiment. The metallic bipolar plate sample which fabricated by rubber pad forming was measured by the laser scanning measurement system with the measurement accuracy of 0.02mm. The result of the measurement represents that, the filling percentage of the bipolar plate is perfect. And the plate is not warped and cracked; the surface quality of the bipolar plate is high. So, the rubber pad forming process is a feasible method to fabricate the metallic bipolar plate. |
