Process and Equipment of Double-Sided Sheet Hydroforming for Large-Sized Al-Alloy Tailored Shell

In the industrial field,tailored blank forming with aluminum alloy(Al-alloy)has developed fast to meet the demands for large size integrated components with curved surfaces of high precision and with uniform mechanical properties.Traditional forming methods for tailored blank components faced challenges with uneven deformation behaviors and coexistence of rupture and wrinkling defects occuring during the forming process.In this paper,a new manufacturing procedure is proposed with advanced welding and forming technologies for forming integrated shell components.Friction stir welding with post-weld heat treatment was employed to prepare the tailor welded blank and improve its formability prior to forming.A double-sided pressure sheet hydroforming process was introduced to fabricate the Al-alloy tailored blank into a curved surface shell.Finite element modeling was established to analyze the effect of the weld line position and loading paths of stress distributions during the double-sided sheet hydroforming(DSHF)process.A large double-action CNC sheet hydroforming press with tonnage of 150 MN and high pressure liquid volume of 5 m~3 was developed in China.As an application case of the proposed process and equipment,a full-scale tank dome with a diameter of 3 m was successfully hydroformed with a large size Al-alloy tailored blank.It was shown that the DSHF process has the advantages in controlling rupture and wrinkling defects with an Al-alloy tailored blank,and the novel manufacturing procedure enables the production of integrated thin-walled component more competitively than traditional methods.

Mechanics analysis of axisymmetric thin-walled part in warm sheet hydroforming

To obtain the influence of fluid pressure and temperature on warm hydroforming of 5A06-O aluminum alloy sheet, the unified mechanics equilibrium equations, which take through- thickness normal stress and friction into account, were established in spherical coordinate system. The distribution of through-thickness normal stress in the thickness direction was determined. The relation between through-thickness normal stress and fluid pressure was also analyzed in different regions of cylindrical cup. Based on the method of subtracting one increasing function from another, the constitutive equation of 5A06-O applied to warm hydroforming was established and in a good agreement with uniaxial tensile data. Based on whether the thickness variation was taken into account, two mechanic models were established to do the comparative study. The results for the studied case show that the calculated stress values are pretty close according to the two models and consistent with results of finite element analysis; the thickness distribution in flange computed by the second model conforms to the experimental data. Finally, the influences of fluid pressure on the flange thickness and radial stress were analyzed.

State of the Art and Perspectives of Hydroforming of Tubes and Sheets

Hollow parts of high accuracy and high strength can be produced by forming methods using liquid media. Hydroforming of tubes has reached a high standard for small parts (volume some 1000 cm3) and is further developed for larger parts (volume some 10.000 cm3). Processes for hydraulic sheet metal forming are sometimes used for small parts from single sheets These pro-cesses are currently under intensive investigation, which is also true for the processing of double layered sheets Single sheets can be formed using membranes which separate the workpiece and the liquid. This results in interesting possibilities for a part and process integration in one step The forming performance of aluminum alloys can be enhanced by using a heated liquid media when forming without membranes.

Developments of New Sheet Metal Forming Technology and Theory in China

Developments of new sheet metal forming technology and theory in China are reviewed in detail in this paper.Advances of crystal plasticity on the deformation mechanism of Mg alloy are firstly described, especially its applications on the prediction of sheet forming process. Then, a new macroscopic constitutive model is introduced, which possesses an enhanced description capacity of tension/compression anisotropy and anisotropic hardening. In order to take into account the twinning process of hexagonal close-packed material, a modified hierarchical multi-scale model is also established with adequate accuracy in a shorter computational time. The advanced forming limit of sheet metal, mainly about aluminum alloy, is also investigated. Besides the above theory developments, some new sheet metal forming technologies are reviewed simultaneously. The warm forming technology of Mg alloy is discussed. New processes to form sheet parts and to bend tubes are proposed by using hard granules. On the other hand, a new kind of ultra-high-strength steel based on typical22 Mn B5 by introducing more residual austenite and Cu-rich phase to increase the elongation and strength and its novel forming method that integrates hot stamping and quenching participation are proposed. Progresses in sheet hydroforming,press forging and electromagnetic forming of sheet metal parts are also summarized.