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An elliptical die hydraulic bulging test was carried out to explore the forming performance of 2A16 aluminum alloy sheets during hydroforming. By using five groups of elliptical dies with ovality of 1.0, 0.9, 0.8, 0.6, and 0.4, the effects of different pressure rates of 0.02 MPa/s, 0.04 MPa/s, and 0.08 MPa/s on the test results were studied, and different sheets thicknesses of 2 mm and 2.5 mm were also explored, then the equivalent stress and strain values obtained by theoretical calculation were also analyzed. Finally, the complete forming limit diagram (FLD) of the 2A16 aluminum alloy sheet at room temperature was plotted through the elliptical hydraulic bulging test and the uniaxial tensile test under the same test conditions. The results show that as the ellipticity increases, the maximum equivalent stress-strain value of sheets gradually increases; reducing the hydroforming pressure rate or increasing the thickness of the sheet can slightly increase the maximum bulging height of the sheet, but it has no significant impact on the maximum equivalent stress and strain value of this material. There is no noticeable difference in the FLD on the right side, indicating that its FLD is universal for a material.

In this paper, a finite element model is developed for 3000 series clad aluminum alloy brazing sheet to account for temperature and strain rate dependency, as well as plastic anisotropy. The current work considers a novel implementation of the Barlat YLD2000 yield surface in conjunction with the Bergstrom hardening model to accurately model aluminum alloy sheet during warm forming. The Barlat YLD2000 yield criterion is used to capture the anisotropy while the Bergstrom hardening rule predicts the temperature and strain rate dependency. The results are compared with those obtained from experi-ments. The measured stress-strain curves of the AA3003 aluminum alloy sheet at elevated temperatures and different strain rates are used to fit the Bergstrom parameters and measured R-values and directional yield stresses are used to fit the yield function param-eters. Isothermal uniaxial tensile tests and nonisothermal deep drawing experiments are performed and the predicted response using the new constitutive model is compared with measured data. In simulations of tensile tests, the material behavior is predicted accu-rately by the numerical models. Also, the nonisothermal deep drawing simulations are able to predict the load-displacement response and strain distributions accurately. [ABSTRACT FROM AUTHOR]

The objective of this study is to compare the strength of riveted joints fabricated by traditional riveting (with pre-drilled holes) and self-piercing riveting (SPR) for different types of joints. Riveted joints were produced using steel and aluminum alloy rivets and two types of sheet material: 235JR steel sheet and EN AW 6060 aluminum alloy sheet with the following dimensions: length l = 100 ± 1 mm, width b = 50 ± 1 mm and thickness g = 2 mm. For all tested types of riveted joints (pre-drilled and SPR), 5 sets of joints were fabricated, each set containing 6 samples. The sets of joints differed with respect to the number of rivets (1, 2, 3, 4 and 6 rivets), joint type (single-, three- and four-riveted joints) and lap length. For all tested joints, the highest load capacity was obtained for self-pierced riveted joints, while the lowest - for pre-drilled joints with aluminum alloy rivets. In addition, it was found that the shear strength of self-pierced riveted joints is higher than that of aluminum and steel blind rivets.

After aluminum alloy sheet metal parts machining, the residual stress release will cause a large deformation. To solve this problem, this paper takes a aluminum alloy sheet aerospace workpiece as an example, establishes the theoretical model of elastic deformation and the finite element model, and places quantitative initial stress in each element of machining area, analyses stress release simulation and deformation. Through different initial stress release simulative analysis of deformation of the workpiece, a linear relationship between initial stress and deformation is found; Through simulative analysis of coupling direction-stress release, the superposing relationship between the deformation caused by coupling direction-stress and the deformation caused by single direction stress is found. The research results provide important theoretical support for the stress threshold setting and deformation controlling of the workpieces in the production practice.