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Top1. Introduction
As the automobile industry advances, lightweight vehicles are being developed to improve fuel efficiency while increasing the strength of the vehicle’s body and the internal components, in addition to enhancing passenger safety (Jeong, Oh & Cheon, 2016). Among the numerous important components of a vehicle, the seat not only supports the human body, but also has a direct impact on the passenger due to external shocks. Therefore, the seat frame should have sufficient strength (Cho et al., 2013). Through shape and strength design of the seat frame, we are actively developing a new seat that conforms to the automobile test regulations. A study on the optimization of the seat frame made of lightweight material that can replace the typical steel seat frame is necessary.
A lightweight seat frame not only has a reduced mass, but it also has the strength that is appropriate to the material. Thus, the aforementioned factors have stimulated the investigation of lightweight seat frames. Kim et al. (2014) compared the frame stiffness with thickness using high-strength steel (HSS), which has a strength greater than that of typical steel. Kim et al. (2016) confirmed that high-strength plastic materials could be applied to the seat frame to make it lightweight, while achieving a strength comparable to steel. Jung et al. (2010) performed optimization experiments for the seat cushion structure with HSS using design-of-experiment (D.O.E), based on the thickness of the HSS. Kim et al. (2017) conducted a lightweight design for bulk trailers using topology optimization to reduce fuel costs and effectively respond to environmental regulations. Han and Jung (2011), and Hwang et al. (2003) conducted an optimal design using topology optimization for the review of structures that can be lightweight while ensuring the safety of railway vehicles and parts as transportation machines.
In this article, Through the static analysis and topology optimization of the seat cushion frame, suitable materials that can be applied as dissimilar materials were selected. Also, confirmed that the application of dissimilar materials and the weight reduction according to the application ratio were confirmed by using the D.O.E. First, the deformation of the cushion frame was confirmed by static analysis using the person per safety standard. Then, topology optimization of the cushion frame was performed and based on the density ratio, a method to apply three dissimilar materials to a typical cushion frame was proposed. As a result of the analysis of the cushion frame using three dissimilar materials, it was confirmed that the deformation decreased compared to the frame using typical steel, and the application ratio of the dissimilar materials for lightweight optimization was derived. Lightweight optimization using D.O.E revealed that the cushion frame thickness changed depending on the application ratio of the dissimilar materials, which resulted in approximately 10% weight reduction compared to typical steel, and about 30% improvement in strength.