| With the rapid development of China's railway industry, more and more high-speeded, heavy loaded trains and urban railway trains have put into operation. The quality and reliability requirements of the vehicle and vehicle-related products have increased rapidly. Welded structure is the most widely used structure in the railway industry. But, virtually the welding deformation control is essentially the weld quality control, while the weld beam quality control is the most crucial factor of the fatigue life of the weld beam.Welding residual deformation and welding fatigue are two main problems in the weld structure's designing and manufacturing, for it's owe particularity on the manufacturing technology. The welding residual deformation is the crucial influential factor in the design integrality, the rational manufacturing techniques and the service durability of welding structures. But the additional procedures, such as deformation rectification after welding, are expensive and liable to impair the service durability. Therefore, scientific and quantitative prediction of welding deformation regularities, and the optimal quality-control measures, are important theoretical value and engineering significance to the structure integral design, manufacturing technique selection and the safety assessment of welding structures. At the same time, the research has found that welded structure is the key link of the reliability design of rail vehicles, for it is the most vulnerable to rail vehicle fatigue damage. So predict the fatigue life of the welded structure scientifically in the design process and compared the program quickly is exigently needed.Based on the summary of the domestic and foreign studies on welding deformation and fatigue life prediction of welding, a series of investigations were made on railway flat car's center sill and vehicles bogie around the welded structure's fatigue life prediction and the weld deformation simulation. The main contents are outlined below:First of all,the thesis introduces the theory of thermal conduction and the simulation of welding deformation and reliability design criteria and fatigue life prediction of welded structure. And according to the theory, elaborate the welding deformation control through welding ordinal optimization based on"Local-Global"mapping method and the methods of welding sequence optimization thoroughly. The welded structure fatigue life predictions based on the IIW standard were also introduced in this work.Then, the railway flat car's center sill welded structures were analysed and were did the welding sequence optimization using the"Local-Global"mapping method. Designed and completed the four kinds of welded joints which external structure required, according to the center sills structure. Based on the above joint calculate the local model and the global model of the center sill's external weld bead in the software SYSWELD using Gaussian double-ellipsoid heat source model and compared with the experimental results. Optimized the factor which impacted the center sill's welding deformation such as welding materials and welding sequence.Finally, the thesis studied on the evaluating fatigue life for welded structure, and introduce the structural fatigue evaluation systems base on IIW standard and UIC standard load model. In order to facilitate the designers'fast fatigue evaluation, developed the fatigue and techniques design system based on IIW standard, which use Visual Studio 2005 as development platform and use SQL Server 2005 as database platform. The system evaluates the welding structure's fatigue life effectively. This thesis describes the process of concrete realization of the system. and validated the system's engineering practicability with the welded bogie frame. |
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