bending in the different zones which provokes compressive and
tensile residual stresses in the outer and inner layers of the sheet.
This difference in stress between the two layers is in fact the main
reason for Dh1 being greater when the BHF is nil, knowing that Dh1
takes its maximum value of 1.8 mm for a value of Rd equal to 8 mm
Fig. 5. Moreover, the shape of the plot giving Dh1 against the
stretching height h is identical to that presented by Liu et al. [32]
who have shown that springback decreases with the increase of
the height/thickness ratio.
By increasing the value of BHF up to 3 KN, primary springback
Dh1 takes minimum values close to zero. This is due to the fact that
the effect of tension, under the action of tightening, becomes
increasingly important compared to bending. For a higher level
of clamping (BHF > 9 KN), the springback increases again.