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인장전단시험을 이용한 TRIP1180강의 계면파단특성 평가
박상순,최영민,남대근,김영석,유지훈,박영도,Park, Sang-Soon,Choi, Young-Min,Nam, Dae-Geun,Kim, Young-Seok,Yu, Ji-Hun,Park, Yeong-Do 대한용접접합학회 2008 대한용접·접합학회지 Vol.26 No.6
The weldability of resistance spot welding of TRIP1180 steels for automobile components investigated enhance in order to achieve understanding of weld fracture during tensile-shear strength (TSS) test. The main failure modes for spot welds of TRIP1180 steels were nugget pullout and interfacial fracture. The peak load to cause a weld interfacial failure was found to be related to fracture toughness of the weld and the weld diameter. Although interfacial fracture occurred in the spot welded samples, the load-carrying capacity of the weld was high and not significantly affected by the fracture mode. Substantial part of the weld exhibits the characteristic dimple (or elongated dimple) fractures on interfacial fractured surface also, dimple fracture areas were drawmatically increased with heat input which is propotional to the applied weld current. In spite of the high hardness values associated with the martensite microstructures due to high cooling rate. The high load-carrying ability of the weld is directly associated with the area of ductile fracture occurred in weld. Therefore, the judgment of the quality of resistance spot welds in TRIP1180 steels, the load-carrying capacity of the weld should be considered as an important factor than fracture mode.
A Study on the Sheet Forming of the Lower Seat Rail using 1180 TRIP Steel
Oh, Won-Jung,Lee, Choon-Man Korean Society for Precision Engineering 2018 International Journal of Precision Engineering and Vol.19 No.2
The automotive industry is investing great effort to reduce the weight of vehicles to improve fuel efficiency and performance. To develop a lighter vehicle, Ultra high strength steel (UHSS) is being increasingly used, and is the focus of efforts to develop innovative sheet steel with high strength, durability and formability, including projects such as Ultra-light steel auto body (ULSAB) and Ultra-Light steel auto closure (ULSAC). Because UHSS is very difficult to form at room temperature, roll forming and hot forming processes have been proposed. However, the productivity of these processes is significantly lower than cold forming. In this study, a seven step cold forming process is proposed for forming a lower seat rail using 1180 TRIP steel, and was found to be more conducive to productivity than other processes. The design of the proposed forming process was determined by forming analysis and experiment. The forming analysis was carried out using DEFORM software, and the experiments were carried out using a mechanical press machine. The weight of conventionally formed seat rails (DP 980) and the proposed seat rails (1180 TRIP steel) were compared to determine the weight reduction.