Design Of The Optimization System Of Railway Passenger Car With Frequency-Forbidden-Region

With the increment of the railway vehicle' running speed, the performance of the car body' structure is demanded higher and higher. The car body not only has to satisfy the demand of strength and stiffness, but also needs to have good dynamic characteristic, so that its chief natural frequencies could keep off the frequency-bands of the car body' external excitations, avoiding resonance between the car body and its components. At the same time, lighting weight is the major goad of the car body' optimization all the time, so, how to realize lighting weight and keeping the good dynamic characteristic have become an important subject of the quasi-high-speed and high-speed passenger car at the condition that the structure satisfies the demand of strength and stiffness.The natural frequencies are not sensitive index to the change of the structure. So, changing the structure manually as the traditional methods is inefficient and it is hard to get the optimum structure. As experience prove, it is difficult to unify lighting weight and improving the natural frequencies of the structure by traditional methods. At the same time, the traditional methods can handle the relative simple and less design variables structure optimization problems with the frequency-forbidden-region, but, it is not appropriate to the complex structures with vast design variables such as the car body of railway vehicle. Genetic Algorithm (GA) could consider the coupling relationship between different kinds of design variable and solve the combination optimization of different kinds of design variable. But there has no researcher apply it on the optimization design of the structure with the frequency-forbidden-region yet.In this thesis, a method of structure optimization design with frequency constraint is presented, and an optimization system of railway vehicle with the frequency-forbidden-region has been designed based on this method. Taking the optimization of a railway passenger car body for example, the optimization system has been proved and getting an ideal effect. It is proofed that this optimization system can realize the unification of static design and dynamic design. Additionally, the fitness function with frequency constraint has been proved and the conclusions could provide some help to such kinds of optimization design of vast design variable complex engineering structure with frequency-forbidden-region.