Abstract: Thinning ratio distribution in hydro-bulging of tailor-welded tubes with different thicknesses are investigated by using Finite Element Method and experiment methods. Further, reasons of nonuniformity of thinning ratio and effects of thickness ratio, length ratio and strain-hardening exponent n on thinning ratio are investigated. It is revealed that due to the various axial strain and the same circumferential strain on the tube blank, the thickness strain is not uniform. On the thicker tube, the closer to the weld-seam it is, the less the thinning ratio will be. However, on the thinner tube, the closer to the weld-seam it is, the larger the thinning ratio will be. Thickness ratio and strain-hardening exponent n obviously influence the thickness distribution. The larger the thickness ratio and the less the strain hardening exponent n are, the larger the thickness difference between the thinner and the thicker tube will be. The thickness ratio mainly affects the thickness distribution near the weld-seam, while the strain-hardening exponent n affects the whole part.

Key words: Hydro-bulging, Light-weight, Tailor-welded tube (TWT), Thickness distribution