Thickness Demarcation Circle of Double-Cone Tube during Hydroforming

Abstract

The analytic formula of the thickness demarcation circle during hydroforming of double-cone tube is derived by using the mechanical analysis and the total strain theory. The effect of friction coefficient, expansion coefficient, ratio of axial stress to internal pressure, length of feeding zone, and initial thickness of tube on the thickness distribution can be given by this formula quantitatively, and the analytic results were compared with the FEM analysis and experimental results. The results show that with the increasing of friction coefficient, the ratio of axial stress to internal pressure, the relative length of feeding zone, the distance between thickness demarcation circle and tube end decreased, that means the increasing of length of the thinning zone, and with the increasing of relative thickness of tube blank, the distance between thickness demarcation circle and tube end increased, that means decreasing of length of the thinning zone.

New Developments of Hydroforming in China

“…The biggest difficulty to form this part is that there is a small bending radius, which can not be formed from a tube by conventional bending process. 22) Figure 17 shows the hydroformed torsion beam which is hollow component with V-type cross-section. It is successfully formed by using the U-type preform.…”

“…It is successfully formed by using CNC bending, preforming and hydroforming. 22) Figure 16 shows the prototype of a chassis part, which is with 3D axis and several typical cross-sections varying from rectangular, trapezoidal to irregular. The material of 440 MPa was used.…”

“…Effect of forming temperature on the formability of typical aluminum alloy sheet was investigated 22) . Figure 23(a) shows the hydroformed cups at different temperatures.…”

“…Figure 9 shows the hydroformed integral stainless steel inlet. 22) It is a thin-walled component with curved axis and complex polygonal-sections. Eight stamped pieces are needed to make the inlet by conventional stamping and welding process.…”