Investigation into the mechanical behavior and the levelling process of the sheet with sheared protrusions for fuel cell application

Abstract

The current collector, a repeated structure of high sheared protrusions, is a major component of metallic bipolar plates for molten carbonate fuel cells (MCFCs). In this work, four topics, which related to the current collector for manufacturing and commercialization, are discussed. First, in order to minimize defects from the forming process such as local thinning, the preform shape in the three-stage forming process that integrates the slitting process, the preforming process, and the final forming process was optimized. In the simulation of the forming process, the ductile fracture criterion was employed to the user material subroutine VUMAT in ABAQUS/Explicit. The steepest descent method was utilized in the design of the forming process to minimize the effective plastic strain. High sheared protrusions were manufactured without defects from the three-stage forming process by using the optimized preform shape. Next, an efficient method to construct the simulation model of the current collector considering the results of the forming process was introduced. Hexahedral mesh coarsening was first conducted using the simulation results of the three-stage forming process of a sheared protrusion. The effective plastic strain was mapped from the old mesh to the newly generated mesh. The simulation model for the current collector was constructed by duplicating and reflecting the newly generated mesh. For the verification of the proposed method, various numerical examples were investigated. From the examples for verification, it was found that the proposed simulation for the current collector was found to be efficient and applicable to the simulation of the mechanical behavior of the current collector for practical application. Then, the deformed shape of the current collector after springback was discussed based on the large deflection theorem. The current collector is bent, resulting in specific curvature with respect to the size of the metallic sheets after the f...