PSI - Issue 22

B.R. Miao et al. / Procedia Structural Integrity 22 (2019) 102–109 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

106

5

It can be seen that the effect of crosswind on the sides of the train is more significant. In addition to the front of the car or the rear part of the car, the overall pressure on the windward side of the train shows a positive pressure, and the leeward side basically presents a negative pressure. With the increase of crosswind wind speed, the positive pressure on the windward side of the train increases rapidly, and the negative pressure on the leeward side also changes. Relative to the wind speed, the change in the speed of the vehicle is not particularly noticeable for the pressure on the side of the carbody. 3. Optimization method An important means of speed operation not only reduces the traction power consumption, but also achieves a better match between material use and carbody performance. At the same time, the lightweight design of the carbody will reduce the overall or local stiffness of the carbody structure, increase the main frequency range of the forced vibration of the carbody structure, and easily cause the resonance effect by the high frequency excitation received during the operation, reducing the passenger's ride. Comfort and safety of train operation (Perez, R. E., 2004; Yi, S. I., 2008.). Aiming at the established finite element model of high-speed train, the parameterized calculation file of the relationship between the thickness of each component plate and the structural strength, stiffness and dynamic performance of the carbody under typical working conditions is calculated (Tedford, N. P. et al., 2010). The non- sorting genetic algorithm (NSGA-II) is improved to realize the lightweight structure of the carbody while considering the dynamic performance of the carbody in multidisciplinary optimization software platform Isight software. The mathematical model for multi-objective optimization of the intermediate carbody structure of high-speed trains is as follows (MA Tie-lin, 2009 ； Venter, G., 2004): Object function:

   

N

( ) min,

Carbody M x

x R

 

(4)

max

F



carbody1

Where x is the vector of n = 26 design variables. Design variable value:     1 2 , , , , 26 T n x x x x n  

(5)

Constraints condition: Subject to ：   

   

180, 17.8,     v v

1, 2,

max S X D X max

m

v

(6)

1, 2,

m



v

Where ( ) Carbody M x is the carbody mass. F carbody1 is the first-order vertical bending natural frequency of the carbody structure. x is vector of design variables , such as 26 dimensional parameters for the thickness of each component of the carbody structure. S max and D max are the maximum equivalent stress and the maximum vertical displacement of the body structure under load. 4. Numerical example 4.1. Carbody finite element model A typical high-speed train carbody structure is selected as the research numerical example. The vehicle dynamics and various load time histories are calculated by the train rigid-flexible multi-body dynamics model. At the same time, the wind-induced load of the train is obtained by aerodynamic simulation. According to the finite element model of the structure and the characteristics of the structural materials, the quasi-static stress method is used to calculate the dynamic stress data of the carbody under typical load conditions (Gemma, S. et al., 2013). Finally, according to the multi-disciplinary fatigue optimization design method based on multi-body system, the vibration fatigue analysis of the carbody structure is carried out. And the quasi-fatigue life and damage calculation results under various load conditions are obtained.The finite element model can be seen in Fig. 3.