Parameter Optimization in the Thermo-mechanical V-Bending Process to Minimize Springback of Inconel 625 Alloy

The present research deals with experimental and finite element analysis for minimization of springback in the V-bending process for Inconel 625 alloy. Different material properties were determined at three distinct temperatures (303 K, 473 K and 673 K) and deformation speeds (1 mm/min, 5 mm/min and 10 mm/min). Temperature was found to have significant effect on the flow stress of the material. Taguchi analysis was applied to find springback of Inconel 625 by considering four process parameters (temperature, punch speed, holding time and orientation of the sheet) and at the three predetermined levels of settings. Based upon signal-to-noise ratio analysis, temperature (46.93%) was found to be the most influential parameter affecting the springback followed by holding time (26.29%), sheet orientation (24.07%) and punch speed (2.69%). The optimized setting for the minimum springback of Inconel 625 alloy obtained after the conformation test was 673 K temperature, 1 mm/min punch speed, 90 s holding time and 90° to the rolling direction of a sheet. The springback was significantly reduced by 69.63% with the optimized setting of process parameters. The springback factor was also evaluated, and it was found to be directly proportional to the temperature and holding time and inversely proportional to the punch speed, but no particular trend was followed for the sheet orientation as a process parameter. The Arrhenius constitutive model with both Barlat and Hill yield criteria was implemented by adopting user-defined material (UMAT) subroutine for finite element analysis. Numerically computed springback from Barlat criterion was found to be in good relation with the experimental results.