# Study on L-Bending Springback of 45 Steel Leather Cutting Tool Coupled with Local Induction Heating
## 1 Introduction  
Leather cutting is an important component of intelligent manufacturing for automobiles, but its inherent properties make it difficult to process [1]. Die cutting enables leather cutting by preparing specially shaped cutters that avoid carbonizing the cut edge of leather caused by the laser cutting and clogging of the leather surface by water jet cutting [2, 3]. According to the shape of the bending parts, the bending methods of sheets are divided into V-bending [4], L-bending [5], and so on. The L-bending process is widely employed in the creation of seat cross members for vehicle chassis and the production of leather cutting tools [6]. The 45 steel sheets are often used as leather cutting tools and are formed at different angles through a bending process. These bent sheets are used to form leather cutting molds for cutting leather in one piece. However, this process under cold working has a significant springback error since the elastic deformation region seeks to restore its previous shape after the removal of external force. This phenomenon is inevitable because of the inherent property of the metal deformation process and may result in issues, including production delays and unqualified parts [7]. Springback is influenced by variables, including bending angle, the radius of the bending corner, holding time, temperature, sheet thickness, mold gap, etc. [8]. Extensive research has been conducted to elucidate the mechanism of springback during bending and to minimize the negative effects of springback in the sheet-forming process throughprediction or bending compensation [9]. It has been discovered that heating the sheet can effectively reduce the contact pressure and residual stress needed to bend the sheet, increase the formability of sheets, and reduce the risk of the metal sheet rupturing [10]. Global heating and local heating are the two types of heat treatment. The stress change process of the sheet during the bending process is usually obtained using the finite element analysis (FEA) method, which can also make a preliminary prediction of the springback behavior of the sheet. [PERSON] et al. [11] performed shallow-inclined single-point incremental forming of the sheets after global heating and established a finite element model at high temperatures, proving that the redundant deformation zone of the sheet is larger under cold forming. [PERSON] et al. [12] conducted the global heating of the sheet and probed into the bending process of V-shaped dies at different temperatures from 50 \({}^{\circ}\)C to 300 \({}^{\circ}\)C at a bending angle of 60\({}^{\circ}\), indicating that the springback rate decreased as temperature increased, and the minimal value was obtained at 300 \({}^{\circ}\)C. In addition, the high temperature can soften the sheet, lessen strain hardening, lower the convex height of the sheet, and enhance the geometric accuracy. [PERSON] et al. [13] developed elastoviscoplastic models of V-bending and U-bending under global heating and discovered that the low flow stress at high temperatures is mostly responsible for the reduction in springback. Plastic deformation occurs in only a portion of the bent plate; thus, global heating is not necessary. In order to improve the efficiency of thermoforming bending, research on localized heating thermoforming has been carried out [14]. [PERSON] et al. [15] used a heating furnace to globally heat and bend the DP 980 steel sheet and found that when the temperature is higher than 600 \({}^{\circ}\)C, the bending angle exceeds the target angle, which is called the bouncing phenomenon. Furthermore, it has been discovered that the plastic deformation brought on by bending under local heating only affects a very small area, and heating the restricted area is sufficient to reduce the flow stress and reduce springback [14]. Finally, experiments and finite element analysis simulations were used to confirm the viability of local heating. [PERSON] et al.