In order to overcome the technical challenges caused by the high-speed operation of trains, innovative technologies have been applied in the design of high-speed trains in China, such as aerodynamic reduction, aerodynamic noise reduction, airtightness and strength, modal matching, vibration reduction and noise reduction, and lightweight. The use of three-dimensional structures in the internal load-bearing components of the trains has become increasingly popular. This article will explore the application of three-dimensional free bending forming technology in high-speed train manufacturing.
Application of Three-Dimensional Free Bending Forming Technology in High-Speed Train Manufacturing
Three-dimensional free bending forming technology is an important innovation based on three-dimensional trajectory control flexible forming technology, which can achieve accurate forming of hollow components with complex axial lines and complex sections. Since its invention in the 1990s, with the improvement of relevant basic research, commercial free bending forming equipment has been developed by companies in Japan and Germany, and it has been widely used in aerospace, automotive, and especially military industries, receiving unanimous praise.
In the field of aviation manufacturing, Chinese researchers have demonstrated the immense potential of three-dimensional free bending forming technology. In 2014, Yuan Song, a researcher at the Beijing Aerospace Manufacturing Engineering Institute of Aviation Industry Corporation of China, introduced the technology for the first time in China in his work “Aircraft Sheet Metal Manufacturing Technology,” highlighting its potential technological advantages and application prospects. In 2016, Associate Professor Guo Xunzhong from Nanjing University of Aeronautics and Astronautics wrote an article titled “Three-dimensional Free Bending Forming Technology and Its Potential Application in Aircraft Manufacturing Industry,” analyzing and looking forward to the application prospects of the technology in the manufacturing of complex curved components. In 2018, Professor Tao Jie from Nanjing University of Aeronautics and Astronautics systematically introduced the development process, key technologies, and five typical configurations of free bending forming equipment developed by companies such as Germany’s J.Neu, and their mechanism of motion in his work “Three-dimensional Free Bending Forming Equipment and Its Key Technologies.”
Table 1: The Advantages of Three-dimensional Free Bending Forming Technology
|High accuracy||Precise forming of complex axial line and section profile|
|High efficiency||Single-time forming of hollow components|
|High flexibility||Accommodates complex shapes and profiles|
|High controllability||The impact of heat treatment on the shape of components is controllable|
In high-speed train manufacturing, three-dimensional aluminum extrusions are widely used to meet the requirements of lightweight and long service life. AL-Mg (5000 series), AL-Mg-Si (6000 series), and AL-Mg-Zn (7000 series) aluminum alloys are commonly used due to their structural strength, stiffness and lightness, corrosion resistance, easy processing and welding, complex extrusion of hollow profiles, and recyclability. AL-Mg aluminum alloy has good welding and corrosion resistance, but poor extrusion workability. AL-Mg-Zn aluminum alloy was developed for thin-walled and lightweight development, and has good extrusion workability, material strength, and weldability. AL-Mg-Si is a new aluminum alloy material developed to overcome the stress corrosion of AL-Mg-Zn series aluminum alloy materials.
Table 2: Comparison of Different Aluminum Alloys Used in High-Speed Train Manufacturing
|Features||Good welding and corrosion resistance||Good extrusion workability, strength, and weldability||Monogenic solid solution strengthening and increase elongation|
|Suitable for||Components and joints requiring good welding performance||Structural parts with complex sections and profiles||High-precision components requiring high strength and stiffness|
|States||T5, T6||T5, T6||T5,|
To enhance the strength of aluminum extrusions, a heat treatment is often applied to induce desired mechanical and physical properties. The status of aluminum extrusions is mainly classified into the H112, T5, and T6 states. Different aluminum alloy states have different properties, and the impact of heat treatment on the shape of components is controllable. Although H112, T5, and T6 aluminum extrusions have sufficient strength, their forming performance is poor. Therefore, for complex three-dimensional aluminum extrusion profiles, the O-state extrusion can be firstly used for bending, followed by a heat treatment to H112, T5, or T6 which is proven to be feasible.
Three-dimensional free bending forming technology has huge potential in high-speed train manufacturing. The application of this technology can help to produce complex curved components with lightweight and long service life. This article highlights the significance of three-dimensional free bending forming technology and its potential application in high-speed train manufacturing.