Deformation compatibility of hydroforming for tailor-welded tube with dissimilar thickness

Tailor-welded tube (TWT) can be produced from tubes with dissimilar thickness and formed into tubular part with different cross sections through hydroforming to acquire better lightweight performance. To reveal the effect of length ratio and thickness ratio of thicker tube to thinner tube within hydroforming of the TWT, the hydroforming processes were simulated by FEM for TWT with different structure parameters, including length ratio and thickness ratio. The relationship among the structure parameters, strain and thinning rate distributions were analyzed based on the simulated results. Hydroforming experiments were carried out for the TWTs with different length ratio, and then the strain and deformation compatibility were measured and analyzed. The result indicates the deformation compatibility improves with the length ratio increasing and thickness ratio decreasing. Thickness difference causes the significant difference in deformation state on the thinner and thicker tube within hydroforming, consequently the biggest tensile strain along axial direction occurs in the thinner tube adjacent to the weld-seam and induces the severer thinning on the corresponding position. The better the deformation compatibility is, the more uniform the thickness distribution is.