## 2 Finite Element Model
### Chip Separation Guidelines  
The milling process is often accompanied by the continuous removal of material, and the milling cutter continuously cuts the material from the workpiece. The cutting separation criterion is used to judge whether the chips can be separated from the cladding layer. In the ABAQUS finite element simulation calculation, there are mainly geometric and physical separation criteria. The definition of a geometric separation criterion is simple, easy to judge, and stable [30]. When creating the cladding layer milling model, the separation line between the chip and the cladding layer must be established artificially, but the selection of the separation value requires certain engineering practice experience, so the calculation results of geometric separation criteria generally have larger errors and lower accuracy. The physical separation criterion does not need to artificially establish a separation line when modeling, and the calculation results of the cutting simulation are more real and reasonable and more in line with the actual machining process; thus, the physical separation criterion is selected in the simulation calculation.  
For the Ti6 Al4V titanium alloy material milling model, the J-C material damage model was selected, which considers the influences of the stress, strain rate, and milling cladding  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Modulus of** & & **Coefficient of Linear** & & **Coefficient of Thermal** \\
**Elasticity (MPa)** & & **Expansion (\({}^{\circ}\)C)** & & **Conductivity (W/m\({}^{\circ}\)C)** \\ \hline \(6.4\times 10^{5}\) & 0.22 & \(4.5\times 10^{-6}\) & 220 & 75.4 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Tool material performance parameters.  
temperature of Ti6 Al4V titanium alloy wire on material damage. The specific expression is as follows [31]:  
\[\left\{\begin{array}{c}D=\sum\frac{\triangle\overline{\overline{\overline{ \overline{\epsilon}}}}}{\overline{\overline{\epsilon}}^{\overline{\overline{ \epsilon}}}}\\ \overline{\overline{\epsilon}}^{\overline{\overline{\epsilon}}}=\left[D_{1}+D_{2} \exp D_{3}\frac{\overline{\epsilon_{\overline{\overline{\epsilon}}}}}{ \overline{\epsilon}^{\overline{\overline{\epsilon}}}}\right]\left[1+D_{4} \ln\left(\frac{\overline{\overline{\epsilon}}}{\overline{\epsilon}_{0}}\right) \right]\times\left[1-D_{5}\left(\frac{\overline{T}-\overline{T}_{\overline{ \overline{\epsilon}}}}{\overline{I}_{\overline{\overline{\epsilon}}}-\overline{I }_{\overline{\overline{\epsilon}}}}\right)\right]\end{array}\right. \tag{8}\]  
where \(\Delta\overline{\overline{\epsilon}}\overline{\overline{\overline{\epsilon}}}\) is the equivalent plastic strain coefficient increment; \(\overline{\epsilon}^{\overline{\overline{\epsilon}}/}\) is the equivalent strain when the material fails; \(D_{1}\), \(D_{2}\) and \(D_{3}\) are strain related parameters respectively; \(D_{4}\) and \(D_{5}\) are strain rate related parameters and thermal softening parameters respectively; \(\overline{\overline{\epsilon}}_{0}\) is the reference strain rate, which is taken as \(1/\mathrm{s}\) in the calculation in this study; \(\sigma_{\mathrm{m}}\) and \(\overline{\overline{\epsilon}}\) are the average normal stress and the equivalent stress, respectively. Related parameter settings are shown in Table 4.