The clinching process is more and more used in automotive design and manufacturing. Traditional quality inspection of joints needs a lot of destructive tests, which is time-consuming and material-consuming. In this paper, the clinching process and joints failure of dissimilar materials, 6061 aluminium alloy and HC340/590DP dual-phase steel, are studied. A two-dimensional finite element model is established. Experiments were carried out to verify the numerical model. Through the axial tensile test, the quality of clinched joints for upper steel-lower aluminium alloy and upper aluminium alloy-lower steel were measured, respectively, and the strength and safety of the joints met the requirements of design indexes. The conventional prediction model of maximum tensile force and its modified model was researched. Combined with numerical simulation results, the fracture load, the separation load, and the failure mode of two clinched joints were predicted, respectively. Furthermore, the results are in good agreement with the experimental results. The results show that the modified prediction model of maximum tensile force has a good prediction result, and the error rate is less than 10%. The modified prediction model of maximum tensile force can effectively predict the tensile failure test results, which provides a basis for the quality evaluation and strength prediction optimization of dissimilar materials clinched joints.

The problem of springback is one of the most significant factors affecting the forming accuracy for aluminum 3D stretch-bending parts. In order to achieve high-efficiency and high-quality forming of such kind of structural components, the springback behaviors of the AA6082 aluminum profiles are investigated based on the flexible multi-points 3D stretch-bending process (3D FSB). Firstly, a finite element simulation model for the 3D FSB process was developed to analyze the forming procedure and the springback procedure. The forming experiments were carried out for the rectangle-section profile to verify the effectiveness of the simulation model. Secondly, the influence of tension on springback was studied, which include the pre-stretching and the post-stretching. Furthermore, the influences of the bending radius and bending sequence are revealed. The results show that: (1) The numerical model can be used to evaluate the effects of bending radius and process parameters on springback in the 3D FSB process effectively. (2) The pre-stretching has little effect on the horizontal springback reduction, but it plays a prominent role in reducing the springback in the vertical direction. (3) The increase of bending deformation in any direction will lead to an increase of springback in its direction and reduce the springback in the other direction. Besides, it reduces the relative error in both directions simultaneously. This research established a foundation to achieve the precise forming of the 3D stretch-bending parts with closed symmetrical cross-section.