Quasi-static-dynamic formability of AA5052-O sheet under uniaxial and plane-strain tension

An experimental study on the quasi-static-dynamic formability specified in electromagnetically assisted sheet metal stamping(EMAS)was presented.A series of uniaxial and plane-strain tensile experiments were carried out on AA5052-O sheet by using a combined quasi-static stretching and pulsed electromagnetic forming(EMF)method.Failure strains representing formability beyond conventional quasi-static forming limits are observed under both uniaxial tensile and plane-strain states.The total forming limits of the as-received aluminum alloy undergoing both low and high quasi-static pre-straining are almost similar in quasi-static-dynamic deformation.Ultimate total formability seems to depend largely on the high-velocity loading conditions.Thus, it appears that for quasi-static-dynamic deformation,the quasi-static pre-straining of material is not of primary importance to the additionally useful formability.These observations will enable to develop forming operations that take advantage of this improvement in formability,and will also enable the use of a quasi-static preform fairly close to the quasi-static forming limits without weakening its total formability for design of an EMAS process in shaping large aluminum shell parts like auto body panels.

QUANTITATIVE PREDICTION FOR SPRINGBACK OF UNLOADING AND TRIMMING IN SHEET METAL STAMPING FORMING

Based on the elastic-plastic large deformation finite element formulation as well as the shell element combined discrete Kirchhoff theoretical plate element (DKT) with membrane square element, deep-drawing bending springback of typical U-pattern is studied. At the same time the springback values of the drawing of patterns' unloading and trimming about the satellite aerial reflecting surface are predicted and also compared with those of the practical punch. Above two springbacks all obtain satisfactory results, which provide a kind of effective quantitative pre-prediction of springback for the practical engineers.

A Mechanics Model for Stamping a Sheet on Elastic Die with Large Deformation

A semi analytical method was proposed to solve the mechanics problem of stamping a sheet on elastic die. The sheet was divided into four parts according to its deformation and contact with the punch and elastic die. Analytical solutions were derived individually for each part by using elastic large deflection and plastic large deformation. Solutions were found out with MATLAB by developing a numerical algorithm. Interface forces were obtained by iteration under the compatibility conditions between the neighboring parts of the sheet. Computation shows the method is efficient.

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.