Effects of Pre-Tensile Deformation on the Fatigue Fracture Behavior of Annealed 7005 Aluminum Alloy Plate

In the present study, the fatigue life and fatigue fracture characteristics of annealed 7005 aluminum alloy plates subjected to different pre-tensile deformations were investigated. The results obtained upon increasing the pre-tensile deformation of the alloy plate to 20% revealed that the second-phase particles did not show any obvious changes, and that the thickness of the thin strip grain slightly decreased. The dislocation distribution in the alloy matrix varied significantly among the grains or within each grain as the dislocation density gradually increased with increasing pre-tensile deformation. Moreover, the fatigue performance of the annealed 7005 aluminum alloy plate was significantly improved by the pre-tensile deformation, and the alloy plate subjected to 20% pre-tensile deformation exhibited an optimal fatigue life of ~1.06 × 106 cycles, which was 5.7 times and 5.3 times that of the undeformed and 3% pre-stretched alloy plates, respectively. Two fatigue life plateaus were observed in the pre-tensile deformation ranges of 3–5% and 8–12%, which corresponded to heterogeneous dislocation distribution among various grains and within each grain, respectively. Moreover, two large leaps in the plot of the fatigue-life–pre-tensile-deformation curve were observed, corresponding to the pre-tensile deformation ranges of 5–8% and 16–20%, respectively.

Numerical investigation of the effect of hole reaming on fatigue life by cold expansion

The reaming process of the 6061 aluminum alloy plate after cold expansion with split sleeve was simulated by finite element (FE) method based on Abaqus/CAE, the relationship between the reaming depths and the distribution of residual stress fields is obtained by analysis. The fatigue lives of the plate under different reaming depths were calculated by using the fatigue analysis software FE-SAFE, and verified by fatigue tests. The results show that reaming after expansion will increase the residual compressive stress at the hole edge on the entrance surface. In addition, the fatigue life of the specimens increases with the increase of the reaming depth, and the best fatigue gain of the specimen is obtained when the reaming depth of 0.5 mm.

Model-based Intelligent Recognition for Aluminum Plate Seam Defects

In order to study the application of nonlinear ultrasonic in the quantitative identification of defective aluminum plate, different depth cracks are machined on the aluminum alloy plate with a thickness of 10 mm by wire cutting to simulate the defects in the plate. The normal and defective aluminum plates are selected to establish the experimental model, and the continuous wavelet transform (CWT) is used to extract the characteristic parameters of the aluminum plate nonlinear ultrasonic signal. The dimensions of the data are reduced by principal component analysis (PCA), and the principal component with the top three contribution rate are selected as the characteristic value. Finally, the support vector machine (SVM) algorithm is used to analyze the aluminum alloy plate state and classify the defect signal. The experimental results show that the feasibility of nonlinear ultrasonic signal recognition of aluminum plate defects is verified by combining principal component analysis and support vector machine model.

Effect of Residual Aluminum Thickness on Microstructure and Strength of Friction Stir Spot Welded Aluminum Alloy/Copper Lap Joint

Dissimilar metal lap joining of A5052 aluminum alloy plate and C1100 pure copper plate was performed by using friction stir spot welding. The rotating welding tool, which was composed of a probe part and a shoulder part, was plunged from the aluminum alloy plate which was overlapped on the copper plate, and residual aluminum alloy thickness under the probe part of the welding tool after plunging of the welding tool was controlled in the range from 0 mm to 0.4 mm. The strength of the welding interface was evaluated by using tensile-shear test. Microstructure of the welding interface was examined by using an optical microscope and a field emission scanning electron microscope. The welding was achieved at the residual aluminum alloy thickness under the probe part of the welding tool below 0.3 mm. The welded area was formed at aluminum alloy/copper interface located under the probe part of the welding tool, and its width increased with decreasing the residual aluminum alloy thickness. A characteristic laminate structure was produced in the copper matrix near the welding interface. In the joint fabricated at the residual aluminum alloy thickness below 0.1 mm, hook of Cu was formed at edge of the welded area. The fracture did not occur at the welding interface. A remarkable improvement in strength was observed in the joint fabricated at the residual aluminum alloy thickness below 0.1 mm. The formation of laminate structure and hook is considered to result in joint strength improvement.