A hydro-bulging mechanism of tailor-welded tubes with dissimilar thickness

Abstract

To reveal the deformation characteristics and influence of dissimilar thickness on hydro-bulging of tailor-welded tubes (TWT), a finite-element analysis (FEA), experiments, and a mechanical analysis were conducted. Based on the stress and strain resulting from finite-element simulation, it was concluded that the deformation of the thicker tube lags behind that of the thinner tube throughout the bulging process. The plastic deformation occurs first at the middle zone of the thinner tube and then extends to the thicker tube crossing the weld seam. In general, the expansion occurring on the two parts with dissimilar thickness is non-uniform. However, the higher the length ratio, the higher the deformation compatibility. When the length ratio reaches 0.8, the deformation between two tubes is almost synchronic. It is concluded that the mechanism for improving the deformation compatibility is to induce a deformation in the thicker tube by enhancing the bulging pressure needed for a deformation in the thinner tube by changing the stress state in the thinner tube and applying the work-hardening effect.