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Extruded aluminum profile structural parts in vehicle manufacturing
According to the information, about 60% of the existing orders of European locomotive and vehicle manufacturers are vehicles with aluminum body. 20 years ago, such orders were only 2% - 3%.Now aluminum structure has been applied in ice, tgv-2n, etr460, etr500, Talgo Hotel train and other high-speed trains, as well as many suburban and urban rail transportation vehicles.
The adoption of extruded aluminum profile structural parts began in the early 1970s. At that time, the scientific and technological progress in the application of aluminum profiles had made it possible to make aluminum components according to the required shape and size. This aluminum component has been applied to the tilting car body of apt trains in Britain. However, at that time, the application of extruded aluminum components did not produce great benefits, that is, the higher material prices were not compensated for the reduction of manufacturing workload. At that time, the use of large-size structural parts only reduced the production workload of the car body by 40%, and reduced the dead weight of the 26m long car body to 7.5t, while the dead weight of the 26m long steel car body was 11T. In the 1970s, the railway department paid more attention to the calculation of the total cost of the whole service life of vehicles (purchase cost plus operation and maintenance cost). They realized that the consumption of train traction energy must be maintained at the same level, which largely depends on the self weight of rolling stock.
Later, some new technical and technological measures, the most important of which was achieved in the mid-1980s, such as the adoption of the extrusion method of large-size structural parts of double-layer shell, which reduced the need for transverse fixings to a minimum, further reduced the production time of vehicle aluminum body, reduced by 50% compared with steel vehicles, and it has been possible to make double-layer cylinder body according to the conventional method, and then the opening of window holes Welding operations are all completed in the process of unified technical operations, only partially using robot technology and equipment.
Now, when the railway departments gradually and more reduce their participation in the development of new vehicles and implement purchase policies in order to reduce the initial manufacturing costs and future operating expenses, manufacturers have greater freedom in adopting new structures and materials to meet the technical requirements of subscribers and adapt to the development trend of the market. The extruded aluminum profile structural parts also have other advantages in meeting some strict requirements for vehicle structure. For example, the stiffness of the double-layer shell extrusion structure can ensure that the aerodynamic impact produced when the high-speed train meets has special impact strength. Another important feature of the car body with this structure is its great longitudinal stiffness. The ratio of longitudinal and transverse stiffness can reach 70:30, while the ratio of steel car body is 40:60. In addition, aluminum profiles can also meet the requirements of good external shape, without the use of fillers and a lot of manual work. For example, for some models of German Federal Railway, since no filler is used, after calculation, together with the paint coating, the self weight can be 500kg.
The use of extruded aluminum profile structural parts also makes vehicle manufacturers face complex tasks. They must find a balance between labor and material prices, and make designers strive to achieve this balance. It should be clarified that material is only one factor in the whole concept. The production process and technical process adopted should also be formulated in detail to make it conform to the production capacity of the enterprise and balance with the investment.
For example, for most machine manufacturing companies, minimizing the reserves of means of production is a top priority. The choice of materials and processes by designers has a significant impact on this. ABB has a production line that can produce 8 vehicles with aluminum body every week, which reduces the total cost of material storage by 8%. However, this balance is easily destroyed due to the changes in the technical process caused by the use of materials. For example, when the transition from welding to bonding requires more daily reserves to compensate for the considerable time required for bonding hardening.
Another leading supplier of aluminum profiles for rolling stock manufacturing is Germany's VAW company. The leaders of the company foresee that there is a great development trend in the standardization of vehicle structure and the adoption of module design method (this trend has been strengthened due to market demand, so it has the support of manufacturers), and believe that considering the market demand for the regionalization of local railway transportation in Germany, some private companies will pay more attention to using standardized module structure to meet the requirements of individual orderers to a greater extent. At present, various European locomotive and vehicle manufacturers have a large number of design ideas, and these ideas are based on module design. This transformation to standardization and modularity is beneficial to both producers and users. The expansion of the use of aluminum profiles in vehicle manufacturing will greatly reduce the production cycle due to the wider use of automatic welding.
It is also obvious that welded aluminum body vehicles have high impact load resistance, which is conducive to improving driving safety. ABB invested 1million pounds to organize and carry out the destruction test of aluminum structure, and obtained satisfactory and more importantly, the expected test results. The company has also accumulated valuable practical experience in repairing the fault methods of accident vehicles. At the beginning of 1994, the damage test on the double deck passenger car test sample of tgv-2n train ordered by GEC Alstom in France proved that when the impact force was 250t, due to the absorbed impact energy of 8mj, the structure was extruded for a total of 80cm, and the aluminum body remained intact as a whole.
At the same time, the recognition of the advantages of aluminum car body is not without problems. The steel body locomotive and vehicle manufacturers expressed concern about the emphasis on aluminum in the manufacturing process of ice trains in Germany, and carried out a study to confirm the superiority of steel in 1994. However, as before, the use of steel structure leads to an increase of about 20% in the dead weight of the car body.