# Study on L-Bending Springback of 45 Steel Leather Cutting Tool Coupled with Local Induction Heating
## 4 Discussion and Conclusions  
In this study, the induction local heating technique was introduced to assist in manufacturing L-bending leather cutting tools made of 45 steel. The forming angle and springback behavior under different temperatures and bending angles were investigated through both FEA simulation and experiment. The springback mechanism was also investigated by simulation and discussed. The detailed conclusions are as follows:  
(1) In order to simulate the bending process of the sheet at room temperature and local heating at 800 \({}^{\circ}\)C, an FEA model was developed based on the VOCE hardening model and von Mises yield criterion. The accuracy of the model was verified by experiments, and the maximum errors of the simulated value and experimental value at room temperature and 800 \({}^{\circ}\)C local heating were 5.78% and 3.91%, respectively. (2) The simulation and experimental results show that the forming performance of the sheet under local heating at 800 \({}^{\circ}\)C was improved, and under the same outer mold rotation angle, the forming angle of the sheet increased by 2-6\({}^{\circ}\) in comparison to room temperature. The local heating also reduces the springback amount of the sheet. The local heating also decreases the sheet's springback amount, with the maximum springback amount decreasing by 75.2%. (3) The sheet's springback amount is affected by two main factors, which are the dominant elastic deformation in the bending areas and the imbalance of the tensile and compressive stresses. At room temperature, the springback amount of the sheet with the increase in the bending angle shows the law of decreasing first and then increasing. When the bending angle is less than 45 \({}^{\circ}\), the elastic deformation area of the bending area accounts for a larger area; when the bending angle is larger than 45 \({}^{\circ}\), the plastic deformation area tends to stabilize, and the imbalance of tensile and compressive stresses is a major factor affecting the springback. And as the bending angle increases, the tensile and compressive stresses will be more unbalanced, which will lead to an increase in the amount of springback. The sheet's ability to be formed has significantly improved under a local heating of 800 \({}^{\circ}\)C. The amount of springback brought on by elastic deformation is minimal. The  
Figure 11: The maximum residual stress level of the sheet before and after unloading at room temperature and local heating. sheet's unbalanced tensile and compressive stresses are the primary causes of springback. And the amount of springback rises as the bending angle increases. (4) The sheet's springback rate declined as the bending angle increased at various temperatures, and it was lower when the sheet was heated locally. The springback rate at room temperature and local heating decreased from 20.8% and 5% at bending 15\({}^{\circ}\) to 2.9% and 1.4% at bending 90\({}^{\circ}\), respectively. In addition, local heating significantly lowers the sheet's residual stress level relative to room temperature. However, due to various factors, there are some shortcomings in this study that need further improvement and in-depth analysis and research. The next steps of future work can be carried out from the following aspects:  
1. The FEA carried out in this study adopts a relatively single VOCE hardening model, and the simulation results obtained and the experimental results still have errors. Researchers can try to use other hardening models (e.g., Hollomon, Ghosh, Swift, etc.) to make comparisons to ensure that the highest simulation accuracy is achieved. 2. This study only utilizes the finite element simulation of the sheets springback analysis, the analysis method is relatively singular. In the future, the microstructure of the bending place can be studied to further analyze the rebound mechanism. 3. The bending angle experiments carried out in this study did not analyze the actual springback angle compared with the simulated springback angle.