Papers by Keyword: Thin Metal Sheets

Abstract: Joining of very thin metallic foils is required in vast applications such as fuel cell plates, micro reactor carriers, heat exchanger etc. Pressure welding is found to be an efficient method. However, some metals (e.g., stainless steel) are difficult to achieve successful solid state bond at room temperature. In present study, a novel electric assisted pressure welding (EAPW) process was proposed. In the EAPW process, electric current was introduced to the metal sheets under pressure welding in the purpose of reducing welding difficulty. An EAPW experimental setup was developed to study the joining process of Stainless Steel (SS) 316 sheets. The effects of electric current as well as process conditions on the final bond strength were experimentally studied. It was found that SS316 sheets could not be bonded without current at room temperature. However, they were successfully joined with electric current introduced. The co-effects of temperature and electric current were also investigated experimentally. It was found that elevated temperature caused by Joule heat is not the only reason for the improvement of the welding performance. The so-called electro-plastic effect also makes a contribution in EAPW process. Finite element method (FEM) was also employed to analyze the process and the welding behavior was discussed.

Abstract: Bipolar plate is the key component of proton exchange membrane (PEM) fuel cell and represents a significant part of the overall cost and the total weight in a fuel cell stack. The thin sheet metal, with usually 0.1~0.3mm thickness, deformed to bipolar plate with flow channel 0.5~2mm width and depth, by rubber pad stamping can reduce the cost greatly. The rubber pad is simulated by solid element and hydraulic pressure respectively. Experiment shows that the hydraulic pressure can simulate the rubber pad. The thin sheet metal is modeled by solid element and shell element respectively. Considering thin sheet metal material size effect, the shell element cannot simulate the thin sheet metal stamping process because of small corner radius. Modeling rubber pad by hydraulic pressure and thin sheet metal by solid element, the simulation of the rubber pad stamping process shows that 1) the sheet metal in channel appears large uneven strain with high stress; 2) convex fillet make the sheet metal two direction tensions and should keep large fillet corner. Those simulations are validated by experiments. The research on rubber pad stamping will improve the understanding of this micro forming process and provide design guide of flow channel.