Study on wrinkling behavior in hydroforming of large diameter thin-walled tube through local constraints

Large diameter thin-walled tubes are prone to wrinkle due to a low stability of anti-wrinkles, non-uniform material flow, and contact sequence to the die cavity during hydroforming process. Although wrinkling defects can be controlled by reducing the diameter of the initial tube to some extent, the severe thinning will occur. A method of using local constraints was proposed to eliminate wrinkling defects that occurred on thin-walled hydroformed tubes. The effect of axial constraint, hoop constraint, and axial-and-hoop constraint on wrinkling behavior of large diameter thin-walled tubes has been investigated by using numerical simulation and experiment methods. In addition, the trajectory of principal stress of the wrinkling zones with different local constraints has been discussed. The results show that axial compressive stress of the two wrinkling zones can be reduced by 6.8 and 23.0% by using axial constraint, respectively. Hoop constraint reduces axial compressive stress by 11.7% at the two wrinkling zones. And the axial compressive stress remarkably decreased by 22.3 and 31.8% using axial-and-hoop constraint. The results reveal that the application of local constraints can effectively restrict the occurrence of wrinkle by decreasing axial compressive stress during hydroforming of large diameter thin-walled tubes. Finally, a desired part without defects has been manufactured successfully by axial-and-hoop constraint.