Springback characteristics of tailor-welded strips in U-draw bending

Abstract

The purpose of this study is to investigate the springback characteristics of tailor-welded strips in U-draw bending. Two different welded strips were adopted to compare the effects of weld-line locations on the springback. One was welded along the centerline of the strip-width and the other was welded along the centerline of the strip-length. To investigate the effect of different thickness combinations on the springback, the tailorwelded strips were joined by a laser welding process. Three sheet thickness combinations were assessed, SCP1 0.8 t * SCP1 1.2 t, SCP1 0.8 t * SCP1 1.6 t and SCP1 0.8 t * TRIP 1.0 t. Three punch profile radii of 3, 6, and 9 mm and three die profile radii of 5, 10, and 15 mm were prepared and three blank holding forces (BHF) of 125 kgf, 250 kgf, and 500 kgf were applied to investigate the effects of punch profile radius (Rp), die profile radius (Rd), and BHF on the springback of tailor-welded strips. With consideration for the thickness of the sheet and the material properties, the extent of the springback on the sidewall of unloaded sheet shapes increases as the thickness and the yield strength of the sheet increase in the U-draw bending process. For longitudinally welded strips, the amount of springback of the TRIP steel sheet in TWB could be reduced through a springback combination of the thinner side and weld-line. For the thinner side (0.8 t) of the centrally welded strips, the deformed shapes after the springback were almost the same regardless of the thickness combination, and the extent of the springback decreased compared with that of non-welded SCP1 0.8 t. Some experimental results are compared with analytical results obtained by using the finite element method.

Experimental and numerical investigations on springback in V-bending of tailor-welded blanks of interstitial free steel

“…It was suggested that for accurate prediction of springback, inclusion of weld zone should be addressed in further studies. Seo et al 17 investigated the effects of punch and die profile radii and blank holding force on springback behaviour of TWBs in a U-draw bending operation. It was observed that springback in both transverse and longitudinally welded strips reduced with an increase in blank holding force.…”

Analytical prediction of springback in bending of tailor-welded blanks incorporating effect of anisotropy and weld zone properties

“…The prediction of springback behaviour of a TWB is more complex than a conventional blank due to the differences in properties or thickness and the presence of the weld. A few studies [13][14][15] have been carried out to characterize the springback phenomenon in TWBs. Chang et al 13 studied the effect of punch profile radius on springback in TWBs with weld line oriented in transverse and longitudinal directions in U-bending.…”

“…It was concluded that springback in longitudinally welded TWB specimens was similar to that of the springback in thicker parent blank. Consequently, Seo et al 15 investigated the effects of blank holding force on the springback behaviour in TWBs in a U-bending operation. Albut and Brabie 16 studied the effect of rolling direction (RD) in U-draw bending of TWBs having the bend axis parallel to weld line.…”

“…The prediction of springback behaviour of a TWB is more complex than a conventional blank due to the differences in properties or thickness and the presence of the weld. A few studies 13–15 have been carried out to characterize the springback phenomenon in TWBs. Chang et al.…”

Prediction of Springback in Long Channels

“…Differences in springback due to thickness were also observed. It was noticed that the springback on thicker side decreased because of the combine springback effect on thinner side and weld line [18]. Differences in material properties provide different springback due to similar blank holding force, and thus, the control force would be needed for a symmetric part [19].…”