基于三维数字图像相关法的管材胀形试验

The constitutive equation and the forming limit diagram are effective means for evaluating the deformability and formability of the metal material. Compared with the traditional tube mechanical properties test, the Tube Bulging Test (TBT) can be used to get more accurate constitutive equation and forming limit of the tube under the action of fluid force. To overcome the problems of mesh distortion and difficulty in axial profile measurement with the traditional method, the 3D Digital Image Correlation method (3D-DIC) was used to obtain and reconstruct the bulging contour of the 5A02 aluminum alloy tube. A mechanical model of the free bulging region of the tube was established, a calculation formula of wall thickness distribution in the bulging region of the tube was given, and the constitutive equation of the alloy was obtained. The results were compared and verified by the finite element method. It is found that the maximum relative error of the power exponential constitutive equation is less than 10%, the maximum relative error of the contour is less than 1.5%, and the maximum relative error of the wall thickness is less than 2%. Finally, the left Forming Limit Curve (FLC) of the tube was obtained by controlling the aspect ratio of the free area.