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Mechanical clinching technology for joining aluminium alloy sheets has been a hot research topic in recent years. However, the clinched joint has a lower static strength than the welded joint and self-pierce riveted joint. In order to increase the strength of the clinched joint, a height-reducing method was investigated in the study. The material of the sheets is AL5052 which is widely used on the automotive body. Extensible dies were used to produce the clinched joint, while a flat die and a bumped die were used to produce the height-reduced joint. In the height-reducing process, the protrusion of the clinched joint was compressed by the flat die. The material of the protrusion flowed to the neck, which increased the strength of the joint by increasing the neck thickness. Different joints with different geometrical parameters were used to conduct the cross-tensile tests. The cross-tensile strength, energy absorption, failure mode and geometrical parameter of the joint are investigated. The results show that the cross-tensile strength and energy absorption of the joint can be increased by the height-reducing process. The main failure mode of the joints is neck fracture mode. The height-reducing method can increase the neck thickness with the decrease of the protrusion height. The height-reducing method was proved to be effective for increasing the strength of the clinched joint. [ABSTRACT FROM AUTHOR]

The high protrusion on the clinched joint affects the appearance of the joint. A height-reducing method was investigated in the work to reduce the protrusion height. The clinched joint was produced with AL5052 sheet and AL6061 sheet. Flat dies were used to conduct the height-reducing process in the experiment. A rivet was used in the height-reducing process to control the material flow of the protrusion and increase the strength of the joint. The cross-tensile strength, tension-shearing strength and energy absorption were investigated in the study. The cross-tensile strength and tension-shearing strength of the joint can be increased by the height-reducing method. The neck thickness also can be enlarged with the reduction of the protrusion. The height-reduced joint can absorb more energy than the clinched joint in the failure process. The height-reducing method was effective for reducing the protrusion height and increasing the strength of the joint produced with different sheets. [ABSTRACT FROM AUTHOR]

In order to solve the problems of die and tooling manufacturing and assembling for the foil forming, especially for the foil micro forming, high-pressure water jet forming (HPWJF), a new die-less forming process for foil parts is proposed. In the forming process, liquid medium such as water and oil is utilized as a flexible tool to deform the ultrathin foil. In this paper, the computational fluid dynamics (CFD) software Fluent was used to simulate the water jet generation in the water jet nozzle and high-speed water impacting on a rigid surface. And then, the effects of jetting distance on the jetting pressure were obtained. To measure the precise mechanical parameters of copper foils, a digital speckle test method was used to detect the tensile process. Local bulging experiment was conducted for the copper foil with a thickness of 50 μm. When the inlet pressure is 8.5 MPa, the suitable jetting distance is 40 mm for the 50-μm-thick copper foil. In such conditions, the bulging height of the copper foil is 1.20 mm in the experiment. The fluid-solid coupled method by using Fluent and Abaqus was applied to simulate the deformation of the copper foil. The errors between the simulated results and the experimental values are lower than 10 %. Furthermore, both the experiment and simulation for micro stretching of 30-μm-thick copper foil were performed. The cylinder die with a diameter of 3 mm and a height of 1.5 mm is used to form the copper foil. Results show that the copper foil cracks when the jetting distance is 24 mm, and the inlet pressure is 12 MPa. With the increase of the inlet pressure, the drawing depth of the copper foil gradually increases, and the bottom of the cylinder part thins gradually, and the wrinkling of the flange of the cylinder part becomes more and more severe. [ABSTRACT FROM AUTHOR]