# Verification of Automotive Monopost Seat Strength through Dynamic and Quasi-Static Simulations
## 4 Monopost Seat  
### Dynamic Simulation  
The three-dimensional (3D) model simulation was first planned to reduce the time required for the simulation and to enhance the model accuracy. In accordance with safety performance standards, the actual testing device comprised two body blocks that are used to apply loads. The body blocks consist of shoulder and lap blocks that replace the passenger chest and torso, respectively, as shown in Figure 5. \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Regulation Name** & **EUR ECE R14 [12]** & **North America FMVSS 210/207 [13; 14]** \\ \hline \multirow{4}{*}{Load} & Loading angle & \(10\pm 5^{\circ}\) & \(10\pm 5^{\circ}\) \\ \cline{2-4}  & \multirow{2}{*}{3-POINT} & SHOULDER & 13,500 \(\pm\) 200 N & 13,345 N \\ \cline{3-4}  & & LAP & 13,500 \(\pm\) 200 N & 13,345 N \\ \cline{2-4}  & Inertial load & Seat weight \(\times\) 20 & Seat weight \(\times\) 20 \\ \hline \multicolumn{4}{c}{Holding time for load} & \textgreater{}0.2 s & \textgreater{}10 s \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison of car seat belt anchorage tests in different countries. Figure 5: Finite element model (FEM) model. HyperMesh finite element software was used to generate meshes and simplify the model. The mesh size of the elements was set to approximately 8 mm to ensure the efficiency of the analysis. The size of certain parts needed to be set smaller to improve the reliability of CAE analysis in some key areas [6; 15]. The shell elements were divided using quadrilateral and triangular meshes, while hexahedral mesh elements were used mainly for the solid parts. Given that the upper section of the monopost seat is insignificant for the simulation, a solid model was converted to a shell to reduce the simulation time and simplify the design. The critical components of the monopost seat upper section, including the back frame, bottom frame, and seat belt buckle, were all made from high-strength steel. An LS-DYNA's MAT_24 material model was used for modeling, with a Young's modulus of 219 GPa, a density of 7850 kg/m\({}^{3}\), a Poisson's ratio of 0.3, a tensile strength of 845 Mpa, and a yield stress of 550 Mpa. The back frame and bottom frame have a thickness of 3 mm, while the seat belt buckle has a thickness of 2.6 mm. The seat belt buckle was set as a rigid body and connected to the seat through rigid elements to prevent local over-deformation during loading. In automotive seat dynamics analysis, the shoulder and lap blocks are components used to apply loads. They are modeled as rigid body elements with a shell element type. The bolts around the slide rail are important, and were modeled using solid elements. Because bolts are typically made of high-strength metal and have very small deformations, they can be treated as rigid bodies and modeled using rigid body elements. In LS-DYNA analysis, rigid elements do not participate in finite element calculations, so the size of rigid elements does not affect the analysis time required. The size of these solid rigid bolt elements was set to approximately 2 mm to ensure that the bolts are accurately represented in the finite element model. In addition, bolt pre-tension was not considered in this case. The contact type between rigid bolts and the slide rail was set to frictionless. Other fasteners were simulated using beam elements connected to the parts to be fastened through rigid body 1D elements. The seat belt is a primary restraint system that controls the occupant's motion inside the car during a car crash [16]. The car seat belt is typically made of synthetic materials, such as polyester, nylon, or a combination of both, which have high strength, durability, and abrasion resistance. These materials can withstand high tensile forces without breaking or overstretching, which is crucial for ensuring passenger safety during a collision. This study used a combination of 1D and shell elements to model the seat belt, and rigid body connections were employed to link the two.