Study on springback from thermal-mechanical boundary condition imposed to V-bending and L-bending processes coupled with infrared rays local heating

This paper shows differences of thermal-mechanical boundary condition and springback between V-bending and L-bending processes. Although a recently conducted study showed that an infrared (IR) local heating method substantially reduces springback of dual-phase (DP) 980 steel sheet in V-bending, its application to L-bending, which is one of widely used forming processes in industrial applications, has not been sufficiently reported. In the L-bending experiment conducted in this work, springback does not sufficiently decrease as much as it does in the V-bending test, even though the sheet is deformed under the same temperature condition. For analysis of the difference in springback, thermo-elastic-plastic simulation for both V-bending and L-bending processes were conducted. The numerical analysis shows that the V-bending and L-banding processes have significantly different thermal and mechanical boundary conditions even though both processes go through a bending deformation. The differences in the boundary conditions have a strong effect on the thermal-mechanical behavior of the blank, so that the springback results are different between the two bending processes. Finally, it is also shown that the L-bending process requires a higher temperature condition than the V-bending process in order to sufficiently reduce springback.