| Since3D curved aluminum structural parts can provide a lightweight, space-saving and excellent aerodynamic body structure for vehicle applications, more and more design engineers tend to adopt3D components to improve their products" performance.3D curved parts have drawn a growing attention in vehicle manufacturer fields. However, due to the complexity and difficulty of the3D bending process, the development of the3D curved parts was restricted in past years.In order to achieve a fast, precise and flexible forming technology for3D curved parts, and to meet the urgent needs of the3D bending components using for Chinese high-speed trains manufacturer, a new flexible3D stretch-bending process(FSB) was purposed in this paper. Base on the discrete multi-points dies(MPD) and the idea of flexible forming, the flexible fundamental unit(FFU) and the multiple degrees-of-freedom(DOF)3D stretch-bending manipulator are designed and implemented in this new process. Besides, the phototype of the FSB equipment is developed. According to the superimposed deformation theory, the3D forming of the workpiece is decomposed into horizontal and vertical deformation components, which step-by-step achieved the forming process of complex3D curved aluminum parts. Furthermore, the key technologies of FSB process such as the adjustment technology of FFU, and the shape control method of forming parts are studied in this paper. The analysis methods of theoretical analysis, numerical simulation and experiments verification are all adopted in these research.In the research of automatic adjustment technology of FFU, the serial adjustment technology is emploied in the horizontal direction, and the parallel adjustment technology is adopted in the vertical direction. The corresponding adjustment mechanism are designed and developed. The framework of adjustment control system is build up. The adjustment control units are designed, which are composed of DSP2812and stepper motor in the horizontal direction, and STC89C52and DC motor in the vertical direction. The control program is written adopting the master-slave communication mode. The efficiency of adjustment is improved more than60%by the automatic adjustment technology. In addition, with the vertical adjustment units are replaced by a set of hydraulic system, another new3D bending process combine with horizontal stretch-bending and vertical press bending is realized. Based on this modification, a more complex W-shape3D bending is achieved.Moreover, the mathematic model describing the shape of the forming part is established. The calculation method of the process parameters, such as adjustment parameters of FFU and the trajectory of the clamp are determined, which are the key parameters to control the final shape of the forming part. The evaluation system of3D springback for the FSB process is build up, and the corresponding detector is developed. Based on the analysis of the axial stress and strain status, the theoretical analysis model for3D stretch-bending process is established, which provide a springback calculation method for the forming parts after forming and unload process. The agreement of experiments, simulation and analysis proves the analytical model and the simulation model achieved satisfactory springback predict results. The3D bending experimental results show that with the magnitude of the vertical deformation increases, the amount of springback deformation will reduce in the horizontal direction.At last, according to the measured springback data, a direct springback compensation method for the MPD’s envelop surface is purposed and studied in this paper. Take the head’s component of high-speed trains for example, the envelop surface of MPD is optimized using the CAE simulation method. The contour error is reduced from1.01%to0.06%by this compensation method. The actual measured contour error is0.05%by the experiment, which achieved accurate forming of the3D bending parts. At present, the FSB process and equipment have implemented industrialized production. |
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