In this study, the electrochemical characteristics of fuel cell were evaluated after applying a compressive load to the activation area of membrane electrode assembly (MEA) in polymer electrolyte membrane fuel cells. The effects of the pressed area under the compressive load were systematically investigated using polarization curves and electrochemical impedance spectroscopies (EIS) of the fuel cell. Interestingly, the performance of the fuel cell was improved as the pressed area of the MEA was increased from 25.2% to 100% of the active area. In addition, the increased pressed area led to a decrease in the ohmic resistance and the activation resistance of fuel cells.

The main shaft of a mechanical press inevitably includes significant stress concentrations that can trigger severe mechanical damage and finally lead to failure under repetitive use. In this study, an efficient procedure to quantitatively evaluate the fatigue life of the shaft system including the main shaft and its support bearings, based on the macroscopic failure analysis of the main shaft broken during actual use, was investigated. For this purpose, the bearing support was modeled as an elastic foundation, and the elastic foundation stiffness value was varied to determine the optimal value that best simulates the failure behavior, especially with respect to the failure location and failure sequence, of an actual shaft. While the finite element mesh size was kept the same, only the effect of elastic foundation stiffness was investigated. The optimum value for the main shaft investigated in this study was approximately 60 N/mm³, and the fatigue life of the shaft was evaluated based on the conventional maximum principal stress theory. Based on this, two modified designs to enhance the fatigue life of the existing shaft are proposed.

To secure the precision forming capability of a press while reducing its production and transport costs, the development of stiff and lightweight frame is important. In this study, the topology and multi-objective structural optimization problem of a frame structure was introduced with an effort to develop highly stiff and lightweight frame for a mechanical press with 300 ton capacity. First, a design space model was constructed to derive a new frame structure different from the existing one for topology optimization. Using the design of experiments and the structural analysis model of the frame structure improved based on the topology optimization result, the multi-objective optimization problem was established with loop stiffness and mass of frame as objectives and the steel plate thickness as design variable. The review on Pareto optimum solutions of the multi-objective optimization problem revealed the fact that this optimization method could significantly contribute to the high stiffness and lightweight frame structure for a mechanical press.