## 2 Structural Optimization Method with Multiphysical Field Coupling
### Finite Element Analysis Method  
As illustrated in Figure 2, three experimental configurations are designed:  
1. Control Group (C0 Group): Unthickened connecting piece and tab, serving as the baseline.
2. Test Group 1 (T1 Group): Thickened connecting piece and tab, used to assess the impact of cross-sectional area on temperature variation.
3. Test Group 2 (T2 Group): Thickened connecting piece and tab, along with welded reinforcement structural part, designed to evaluate the effect of contact area enhancement on temperature changes.  
The comparison between T1 and the C0 isolates the influence of cross-sectional area on temperature rise, while the comparison between T2 and T1 reveals the impact of increased contact area on thermal performance.  
Using the T1 model as an example, this model employs a free tetrahedral grid for three-dimensional discretization, optimizing the grid division scheme through a grid analysis. The final composite grid system consists of 101,920 three-dimensional domain elements, covering areas such as the positive and negative connecting pieces, tabs, and welded reinforcement structural parts; 46,035 two-dimensional boundary elements for surface heat flow exchange; and 6,730 one-dimensional boundary elements to simulate the welding contact lines.  
Figure 1: Flow chart of evaluation methodology.  
Table 1 shows the thermophysical parameters of the conductor structures model. In defining the heat source, the model considers two primary factors: the Joule heat generated by the metal conductor and the heat from contact resistance. For major current-carrying components like the connecting pieces and tab, the Joule heating is calculated based on the theoretical model in Equation (2). For micro-areas such as the welding zone of the piece connector and the contact surface of the welded reinforcement structural part, an equivalent contact resistance model is employed to quantify the interface heating power. The conservation equation and heat transfer law are implemented within COMSOL Multiphysics 6.2 software, with the grid division shown in Figure 3.  
The initial temperature of the structure is set to 25 \({}^{\circ}\)C, which is equal to the ambient temperature. Heat exchange with the surrounding environment is assumed to occur via natural convection, with a convection heat transfer coefficient of 15 w/(m\({}^{2}\cdot\)K). A transient solver is employed to calculate the temperature change in the structure over time under high current conditions. COMSOL software is used to simulate and solve the thermal behavior of conductor structures. The simulation calculates the surface temperature distribution of the structure, considering the Joule heating and heat dissipation mechanisms. The time step for the calculation is set to 0.01 s to ensure accurate temporal resolution. The temperature distribution of Control Group, Test Group 1, and Test Group 2 is simulated under continuous 10 kA discharge conditions.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Structural Parts** & **Density** & **Specific Heat Capacity** & **Thermal Conductivity** \\  & **(kg/m\({}^{3}\))** & **(J/kg\({}^{\circ}\)C)** & **(w/m\({}^{2}\cdot\)K)** \\ \hline Positive connecting piece & 2.7 \(\times\) 10\({}^{3}\) & 8.8 \(\times\) 10\({}^{2}\) & 237 \\ Negative connecting piece & 8.9 \(\times\) 10\({}^{3}\) & 3.9 \(\times\) 10\({}^{2}\) & 394 \\ Positive tab & 2.7 \(\times\) 10\({}^{3}\) & 8.8 \(\times\) 10\({}^{2}\) & 237 \\ Negative tab & 8.9 \(\times\) 10\({}^{3}\) & 3.9 \(\times\) 10\({}^{2}\) & 394 \\ Positive welded reinforcement structural part & 2.7 \(\times\) 10\({}^{3}\) & 8.8 \(\times\) 10\({}^{2}\) & 237 \\ Negative welded reinforcement structural part & 8.9 \(\times\) 10\({}^{3}\) & 3.9 \(\times\) 10\({}^{2}\) & 394 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Thermophysical parameters of conductor structure model.  
Figure 2: Schematic diagram of conductor structure: (a) C0; (b) T1; (c) T2.