# Reliability Analysis of Hybrid Laser INS Under Multi-Mode Failure Conditions
## 2 Mechanical Simulation Analysis of Hybrid Laser INS Structure
### Mechanical Simulation Analysis of the Hybrid Laser INS Structure
#### 2.2.3 Mechanical Simulation Analysis of the Hybrid INS Structure  
Throughout its development, transportation, and operation phases, the hybrid INS structure experiences various shock environments such as engine ignition and separation shocks, explosion shocks, and high-speed aerodynamic shocks during atmospheric re-entry. Shock loads critically affect the strength and stiffness of the inertial group structure. As shock is a complex physical process, assessing structural reliability under shock conditions is crucial. Currently, hybrid INS structural components are primarily made from aluminum alloys. To achieve lightweight, high-precision, and high-overload performance, a well-balanced design of mass and stiffness is challenging. The emergence of SiC/Al composite materials provides a feasible solution. These aluminum-based composites combine metal plasticity and toughness with ceramic properties, offering high strength, high modulus of elasticity, dimensional stability, and good thermal and wear resistance, while addressing the high cost, toxicity, and processing limitations associated with beryllium materials. Table 1 compares SiC/Al composite materials with other commonly used materials. To fully understand the static and dynamic characteristics of the SiC/Al composite structure, this study used a simplified model of the inertial measurement device, as shown in Figure 2, to conduct semi-sine shock and modal mechanical simulations, comparing the performance of traditional ZL107 materials and SiC/Al composites. The conditions and waveform of the semi-sine shock pulse are presented in Table 2 and Figure 8. The comparison results are shown in Table 3. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Performance Indicators** & **SiC/Al** & **ZL107** & **Mg/Al** & **Stainless Steel** \\ \hline Density/(g/cm\({}^{3}\)) & 2.9 & 2.68 & 1.8 & 7.9 \\ Coefficient of thermal expansion & 11–13 & 21.4 & 26.1 & 16.6 \\ Elastic modulus/Gpa & 145–150 & 77 & 40–45 & 184 \\ Tensile strength at break/Mpa & \textgreater{}530 & \textgreater{}220 & \textgreater{}150 & \textgreater{}520 \\ Yield strength/Mpa & \textgreater{}420 & \textgreater{}180 & 140–245 & 275 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison of SiC/Al Composites with other common materials. Figure 7: Internal finite element mesh of the hybrid laser INS structure. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Project** & **Peak Acceleration A** & **Duration** & **Loading Direction** \\ \hline Half sine wave shock & 120 g & 4 ms & \(X\backslash Y\backslash Z\) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Semi-sine shock test conditions. Figure 8: Semi-sine shock pulse waveform and tolerance. As shown in Table 3, the overall dynamic frequency of the SiCp/Al composite structure during modal analysis is significantly higher than that of conventional ZL107 materials, with a first-order dynamic frequency for the SiCp/Al composite at 4336.7 Hz, approximately 14.90% higher than that of the ZL107 material. This suggests that using materials with higher specific stiffness can significantly increase dynamic frequencies. Under the conditions of the semi-sine shock pulse waveform in Table 2 and Figure 8, structural mechanical simulations were conducted on the hybrid INS, and the data are shown in Table 3.  
Comparing structural deformation for the two composite materials, the ZL107 material exhibited the largest deformation, with a maximum deformation of 0.34252 mm on the platform structure, while the inner and outer frames and base experienced minor deformation. The SiCp/Al composite demonstrated a significantly reduced deformation, suggesting greater resistance to plastic deformation failure and higher overload tolerance compared to the ZL107 material. The maximum deformation rate difference for the inner and outer frames between the two materials was \(-\)14.81% and \(-\)14.76%, respectively.