To reveal the deformation characteristics and influence of dissimilar thickness on hydro-bugling of tailor-welded tube (TWT), FEA, experiments and mechanics analysis are conducted. The effects of length ratio, weld-seam movement and work-hardening on deformation compatibility are analyzed. It indicates that the plastic deformation occurs first at the middle zone of the thinner tube, and then extends to the thicker tube crossing the weld-seam. The expansion occurring on the two parts with dissimilar thickness is non-uniform, higher the length ratio and higher the deformation compatibility. Stress-strain analysis reveals that though the whole TWT suffers biaxial tensile stresses and the biaxial elongation occurs in the thinner tube, axial compressive strain occurs in the thicker tube. It is concluded that the mechanism for improving the deformation compatibility is to induce the deformation in the thicker tube by enhancing the bulging pressure needed for the thinner tube through changing the stress state of the thinner tube and flowing stress. Weld-seam movement happens during tailor-welded tube hydroforming, which induces uneven distribution of axial strain and thinning ratio in the TWT.
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