Theoretical Research Of Damage Consistency Load Spectra On Bogie Frame Structures Of High-speed Trains

Loading issues are essential to determine structural reliability and experimental assessment. It is especially difficult to investigate the load spectra of high-speed bogie frames because of their complex structural forms and multisource forces systems. When a train runs at high speeds, the external exciting frequencies approach or exceed the natural frequencies of bogie frames. Strong elastic vibrations may occur. Meanwhile, the correspondence between loads and damage has significant difference with the static case. The present international reliability design criteria and test standard of bogie frames are still in qualitative level, given that a definitive load spectrum is unestablished yet. There is a great difference between prediction and reality. Therefore, it is necessary to establish the load spectra that correspond to damage in service. This research is helpful for improving the reliability design of bogie frames for high-speed trains.In the present paper, the fundamental load series of bogie frames for high-speed trains are constructed. The load measuring method that corresponds to quasi-static deformation modes is studied. The construction method of simplified dynamic load-time histories that correspond to simplified dynamic fundamental load series is presented. The quasi-static load spectra of frame structures are compared with the load spectra that consider dynamic effects. The main contents are described as follows:(1) The fundamental load series of bogie frames for high-speed trains are constructed. The quasi-static fundamental load series that correspond to quasi-static main deformation modes are identified. Based on the vibration theory and the finite element method, elastic dynamic deformation modes that correspond to structural elastic vibration characteristic can be regarded as a combination of each order elastic vibration mode. The fundamental load series that correspond to elastic dynamic deformation modes are constructed.(2) The quasi-static load measuring method of a bogie frame is studied. The quasi-static load measuring system scheme of a frame is designed. A load transducer assembly system of a bogie for a high-speed train is manufactured. The calibration tests for the force-measuring frame are completed through a multichannel loading calibrating experimental bench. Based on calibration data, the load decoupling model of the quasi-static load series is established. Quasi-static load-time histories that correspond to the quasi-static fundamental load series are obtained. The quasi-static discrete load spectra of frame structures are established.(3) The construction method of simplified dynamic load spectra that correspond to simplified dynamic fundamental load series is studied. The simplified dynamic fundamental load series that correspond to elastic dynamic deformation modes are constructed. The computed result proves that the simplified load series can describe elastic modal deformation characteristics. The simplified dynamic load-time histories are obtained. The simplified dynamic discrete load spectra of frame structures are established.(4) Based on the damage consistency criterion and a genetic algorithm, damage consistency calibration of the quasi-static discrete load spectra is performed. Then combination of the quasi-static and simplified dynamic discrete load spectra is calibrated. The damage that corresponds to the quasi-static discrete load spectra is pretty close to the damage that corresponds to the quasi-static and simplified dynamic discrete load spectra. The result indicates that dynamic component of loads has limited effect on structural damage. Therefore, it is enough to just consider the quasi-static loads under current operating conditions, when establishing load spectra of frame structures.(5) Based on measured data from the Beijing-Shanghai Dedicated Passenger Line, load characteristics of frame structures under operating conditions are analysed. The results prove that the track excitations have significant effect on load amplitudes of bogie frames. Dynamic behavior of the quasi-static loads under high-speed operating condition is high frequency with low amplitude. Dynamic values of the quasi-static loads under in-and-out station operating condition are higher than dynamic values under high-speed operating condition. Moreover, the quasi-static loads appear obvious fluctuations and impact.