KEYWORDS vehicle body structure, EV load path, vehicle body structure, low pressure die-casting 1. Research and/or Engineering Questions/Objective : In order to improve the interior UX of EVs, crash energy absorption space has been reduced. On the other hand, the installation of high-voltage batteries has increased the vehicle's crash energy due to increased weight. In order to solve the conflicting risk factors of reduced crash energy absorption space and increased crash energy, this study introduces the development case and discusses the results of utilizing the LPDC(Low Pressure Die Casting) that can increase the strength while integrating parts for the backup load path structure for front and rear collision response of the vehicle. 2. Methodology 1) Selection of casting type : In general, it is known that the low-pressure die casting is difficult to realize thin thickness compared to the high pressure vacuum die casting. In the case of the development vehicle, the CVW level exceeds 2.8 tons. Therefore, even if the high pressure vacuum die casting method is applied to the design, the thickness must be increased to cope with high collision energy. 2) Development : Utilizing the low-pressure casting method, we proceeded with the actual design of the back-up load path related to front and rear collisions. the system level evaluation and completed vehicle level evaluation were conducted, and the countermeasures for the problems encountered in the development process were reviewed, and the actual improvement evaluation and confirmation FEM analysis of the improvement design were conducted. 3. Results : As a result of the actual development of the backup road path utilizing the LPDC, the number of parts was significantly reduced from about 14 to 4EA/vehicle. In addition, the development targets were met in US full frontal, IIHS offset, IIHS small overlap, and FMVSS 301 rear crash evaluations for vehicles with a CVW of more than 2.8 tons. During the development process, the strength of the interface with the energy-absorbing extrusion part was evaluated, and it was further confirmed that the bolted connection showed very stable results compared to the FDS connection. 4. Limitations of this study : This study is a design example for a vehicle with a production volume of less than 5,000 units per year and a vehicle with excessive CVW that makes it difficult to reduce the thickness for the back-up load path body structure parts. As production volumes increase, costs can increase due to the long cycle time of the low-pressure casting process, so this may not be a good example for mass-produced vehicles with fast cycle times. 5. What does the paper offer that is new in the field including in comparison to other work by the authors? : In this study, the world's first frontal collision back-up load path body structure for EV SUV utilizing the low-pressure casting method was designed and evaluated, and it was confirmed that the targeted performance was satisfied. In addition, through the comparison of the advantages and disadvantages of the low-pressure casting method and the high pressure vacuum die casting method, and the comparison with the actual design case, the feasibility of the low-pressure casting frontal collision back-up load path in low-volume vehicles was demonstrated for the first time. 6. Conclusions: To implement the back-up load path for the EV SUV, the low-pressure casting method was selected based on the number of vehicles to be produced and the investment cost of the mold. By utilizing hollow-section design using sand core, a major advantage of the low-pressure casting process, the number of parts in the vehicle was significantly reduced, and the targeted crash performance and static and dynamic stiffness of the vehicle were met.
Mr. JIWOONG PARK, senior research engineer, Hyundai Motor Company