To Set an optimum deformation path for tubular hydroforming, the hydroformi
ng limit of isotropic and anisotropic tubes subjected to internal hydraulic
pressure, independent axial load or torque is firstly proposed based on th
e Hill's general theory for the uniqueness to the boundary value problem an
d compared with those Of the conventional sheet forming. The influences of
the deformation path, the material properties and the active length-diamete
r ratio on the nucleation and the development of wrinkling during the free
tubular hydroforming are also investigated. The above theory is used as a c
riterion and implemented with some new functions ill our ITAS3D, an in-hous
e finite element code for simulating the sheet forming, to control the mate
rials flow and to prevent the final failure modes from occurring. Finally,
the tubular hydroforming of an automobile differential gear box is taken as
an example to show the efficiency and usefulness of the algorithm. (C) 200
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