Weld seam movement of tailor-welded tube during hydrobulging with dissimilar thickness

Finite element analysis (FEA) and experiment were conducted to reveal the reason of weld seam movement and its effects on strain state and thickness distribution during tailor-welded tube (TWT) hydrobulging with dissimilar thicknesses. It is indicated that weld seam movement happens during TWT hydrobulging, and the direction is from the thinner tube to the thicker tube, which induces nonuniform thickness distribution. The different strain states during the bulging process are the intrinsic feature of weld seam movement. Weld seam movement is aggravated by thickness difference between thinner and thicker tubes increase, but is insensitive to weld seam position. When the thickness ratio is bigger than 1.4, movement would concen-tratedly occur during the late period of the hydrobulging process. Such kind of deformation character can bring out local thickness thinning on a thinner tube, but on the contrary for a thicker tube, especially at the zone adjacent to weld seam. Consequently, sharp fluctuation of thickness distribution is brought out near the weld seam, which obviously cuts down fatigue life of the tube component.