ON THE PREDICTION OF SPRINGBACK IN VEE BENDING OF METALLIC SHEETS UNDER PLANE STRAIN CONDITION

P.P. Date (1), K. Narasin-ihan (2), S. K. Maiti (1),U.P. Singh (3)

(1) Department of Mechanical Engineering, IIT Bombay, India
(2) Department of Metallurgical Engineering and Material Sicience, IIT Bombay, India
(3) School of Electrical and Mechanical Engineering, University of Ulster at Jordanstown, NI, UK

Air vee bending of sheet under plane strain Kondition leads to a large amount of springback. A number of models have been developed to predict accurately the springback in bending. Studies on the effect of material parameters on the accuracy of the bending process have been carried out using experirmental and analytical techniques with a view to controlling springback in air bending.

The present work attempts to predict the springback in air vee bending under plane strain conditions taking into consideration the work hardening of the material and superimposed tensile stress. The sensitivity of the springback to the strain hardening exponent (n) was assessed in light of four factors influencing springback, namely, the yield strength of the material ,the superimposed tensile stress, the strength coefficient of the material (K) and the Young's modulus (E). The springback as a function of punch travel (and hence different bend angles) was calculated for two different values of n and the difference in the values of the springback angle was taken as the sensitivity of springback to the n value. This sensitivity was enhanced to various extents depending on the combination of the , K and ciT . lt was found that an increase in K had a pronounced effect on increasing the sensitivity of the n value to springback, followed by and . A high value of K and inconsistent values of material properties could therefore throw light on the inconsistent springback in sheets conforming to standard specifications as variation in springback due to minor variation in the material properties would tend to get enhanced by a high value of K. An inconsistent value of K would make springback highly unpredictable.

A process model was developed for vee bending process to assess the effects of different geometric and material parameters on the springback. The predictions of the model agreed closely with the experimental values in published literature.

Keywords: Springback, Air bending, Metal Forming