Evaluation of springback under the effect of holding force and die radius in a stretch bending test

In this work, we evaluate springback using U-form stretch bending tests. Tests are carried out on aluminum alloy test pieces using an experimental set up made in our laboratory. This apparatus can be mounted on a tensile testing machine and gives the possibility to vary several parameters. We show the role played by certain factors such as die radius of curvature, blank holding force (BHF) and stretching depth. Springback and sliding at extremities are strongly influenced by these technological and geometrical parameters. In this work we also show the gradual decrease of springback with the increase of stretching depth. The radius of curvature of the die can remarkably influence the two stages of springback.

► An original springback device is made.
► An increase in BHF reduces sliding of the sheet and springback.
► The greater the entrance radius of the die, the smaller the final spring back.
► The springback Δθ is negative when the clamping pressure exceeds 8.3 MPa.
► The clamping may play the role of friction between the sheet and the die.