# Experimental and Numerical Studies on the Impact Energy Absorption of Cutting Shear Rings
## 4 Numerical Simulation  
### Finite Element Modeling and Material Parameters  
In engineering practice, metals or fiber-reinforced composites (FRCs) are often used as energy absorption materials. The energy dissipation mechanisms of metals and FRCs are quite different. Metals absorb collision energy through their ductile point through plastic deformation. And FRCs are typically brittle and consume energy through combined fracture mechanisms such as delamination, fiber fracture, and matrix cracking [36; 37]. Compared with FRCs, metals have higher specific energy absorption (SEA), lower design and cost, and meet the requirements of mass production. At the same time, due to the difficulty of recycling composite materials, metal materials have better environmental benefits [38; 39]. Therefore, in most industries, metal materials are used on a much larger scale than FRCs. FRCs are used for specific engineering needs in aerospace, racing, and other industries. Among many metal materials, aluminum alloy is a lightweight structural material with characteristics of high strength, strong corrosion resistance, and good ductility [40; 41; 42], which is widely used in the manufacturing process of energy absorption devices in the manufacturing of vehicles, aerospace aircraft, and other industries. Among many alu  
Figure 5: Impact force–time curve and post-impact rods. (**a**) case 1; (**b**) case 2; (**c**) case 3.  
minum alloy materials, 7075 aluminum alloy has the characteristics of low density, high specific strength, good plasticity, and high impact energy absorption, and it has good comprehensive performance [43; 44; 45]. The 7075 aluminum alloy material was chosen for the energy absorption device. Its chemical composition and mechanical properties are shown in Tables 2 and 3. The method of integrated modeling was adopted in this work. The 3D model was established in SolidWorks, the mesh division and other preprocessing operations were carried out in HyperMesh, the numerical simulation model calculation was completed in LS-DYNA, and the post-processing operations were completed in LS-PrePost. To save the simulation time, the model was simplified to a certain extent. The morphology and critical size of the main components were maintained, and the details of the local position of the members, such as the bump and angle, were ignored. The numerical model consisted of two parts, namely the impactor and the CSR system. The impact part adopted the rigid material model, and it had the same target energy as the weight in the test. The pedestal of the CSR system was made of 45 # steel, and the material parameters are shown in Table 4. To simulate the connection between the pedestal and other devices, full constraints were applied to the back of the base. The energy absorption rods material was a 7075 aluminum alloy with a density of 2810 kg/m\({}^{3}\), an elastic modulus of 71.7 GPa, and a Poisson's ratio of 0.33. The plastic kinematic material model was used to simulate their dynamic behavior. The overall mesh size of the numerical model was 5 mm. In order to improve the simulation accuracy, the mesh near the shear rings was locally encrypted. The transition mesh size was 1 mm, and the shear rings mesh size was 0.5 mm. The Solid Map feature of HyperMesh was used to divide the mesh according to the principle of appeal. The total mesh number of the model is 159,831, and the mesh after division is shown in Figure 6. \begin{table}
\begin{tabular}{c c c} \hline \hline \(\rho\) (kg/m\({}^{3}\)) & \(E\) (GPa) & \(\
u\) \\ \hline
7850 & 200 & 0.30 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Mechanical properties of 45 # steel. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Al.** & **Zn** & **Mg** & **Cu** & **Cr** & **Si** & **Fe** & **Ti** & **Mn** \\ \hline Bal. & 5.80 & 0.04 & 1.40 & 0.01 & 0.07 & 0.18 & 0.03 & 0.05 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Chemical composition of 7075 aluminum ally.