Research and/or Engineering Questions/Objective; The side member of battery case is an important component that determines the crash performance. In particular, the inner-rib of side member with aluminum extrusion is a major design variable that transmits crash energy. For this reason, the topology optimization for side member is conducted to derive optimal shape and position of inner-rib. And the weight increase problem caused by added inner-rib is solved through thickness optimization. Therefore, the objective of this study is to develop the optimized battery case with improved crash performance while maintaining total weight of equivalent level. Methodology; After creating the scaled model of side member for effective topology optimization, structure analysis was conducted to check maximum stress. To derive a scaled model with a 15% stress reduction, topology optimization for inner-rib shape was carried out after setting target stress value. Also extrusion pattern option and minimum thickness value are set to create a regular shape. As a result, an optimized side member shape was obtained and crash analysis of the battery case with optimized side member was conducted. Crash performance was increased in analysis result, but total weight of battery case was also increased because of added inner-rib. Thickness optimization was carried out to solve the problem of weight increase. Firstly, the components to be thickness optimized were selected through the analysis result review about the internal energy and weight distribution of each components. Secondly, thickness optimization was carried out by reducing thickness of the selected components. Results; Through topology optimization about the inner-rib of side member, the optimal side member shape is derived and crash performance is improved. The weight increase problem due to the addition of inner-rib was solved by thickness optimization. Finally, the optimized battery case with improved crash performance while maintaining total weight of equivalent level is derived through topology and thickness optimization method. A prototype was manufactured for reliability test. The main material and manufacture method of prototype were aluminum extrusion, and reliability test was carried out. As a result, it was confirmed that the crash performance was increased. Limitations of this study; Firstly, because the analysis model cannot be configured for the entire vehicle, crash analysis could not be performed under NCAP or IIHS conditions. But after receiving special boundary conditions for battery case unit from OEM, the crash analysis was performed. Secondly, in thickness optimization process, since the minimum thickness that can be manufactured by the aluminum extrusion method is about 2mm, there was a limitation for the thickness reduction. For this reason, the thickness of component is not set to less than 2mm. What does the paper offer that is new in the field including in comparison to other work by the authors? The optimized battery case model was derived through topology and thickness optimization method. Also the reliability of the above optimization methods was verified through prototype test. This optimization methods are hoping to be utilized in various fields. Conclusions; Through the topology optimization of the side member, the crash performance of the battery case is improved compared to the conventional type. Also, the weight of the battery case is maintained at the same level through thickness optimization.
Mr. GeonHee Cheon, CAE Engineer, Seojin Industrial