Study On The Method Of Establishing The Load Spectrum Of Speed-up Passenger Car Bogie Frame

Load spectrum is the basis of reliability design and fatigue test of structure.The research on the preparation of load spectrum at home and abroad involves many fields,but the load spectrum for bogie frame design and fatigue test is relatively low.There are many types of bogie frames for speed-up passenger car,which are widely used and have complicated operating conditions,and safety problems occur from time to time.According to the current international standards,the structural strength and fatigue reliability of bogie frames can only be analyzed at a qualitative level.In order to ensure the safety of railroad transportation,it is necessary to compile a load spectrum that can correctly reflect the operating conditions of the frame structure and upgrade the existing structural reliability design and reliability test evaluation from the qualitative level to the quantitative level for the domestic operating conditions of the frame structure.Correct decoupling identification of the loads is a prerequisite for the development of reliable load spectra.Due to the presence of a series of suspensions(including springs and dampers),the load and strain response of the frame is basically in the low frequency range(less than 10 Hz),while the first order intrinsic frequency of the frame's elastic mode is usually around 30 Hz.In the context of load identification,the dynamic load identification of the frame is basically in the low frequency range.In this paper,the study of bogie frames for speed-up passenger car is based on the current international standards,combined with calibration tests and line measurements,to finally obtain random load spectra and dynamic stress spectra based on line measurements,and to establish a test load spectrum that can be used for bench testing to reproduce road damage.The main focus of the work is on the following.This paper focuses on the study of the load spectrum of bogie frames for speeding passenger train,with the following work priorities.(1)A basic load series analysis of the bogie frame of speed-up passenger car.The completeness of the basic load system of the bogie frame is the basis for the study of load identification and establishment of random load spectrum.Based on the basic load series introduced by the current international standards,the basic load series of the bogie frame is analyzed for the equilibrium force system,the anti-yaw load series is proposed,and the comparison between the predicted dynamic stress of the measured load and the measured dynamic stress verifies the importance of the existence of the anti-yaw load series,which is of guiding significance for the perfection of the load series of other passenger vehicles(such as high-speed rail and subway),so that the basic load series of the bogie frame can cover the deformation characteristics and suspension function of the frame structure completely.(2)The load-stress transfer functions are obtained for the bogie frame at quasi-static conditions.In the laboratory,a quasi-static calibration test is carried out on the frame load system by means of a frame calibration test rig,and the identification method is tested several times to optimise the decoupling process of each load system.The pathological properties of the load recognition transfer matrix of the frame are controlled to ensure that the transfer matrix is well characterised by controlling the number of conditions in the transfer matrix,thus effectively controlling the load recognition errors.(3)Validation of the load identification method.The bogie frame structure is complex and has the characteristics of low damping,which is subjected to many loads with high coupling and significant low frequency characteristics.In this paper,the quasi-static calibration method is used to determine the bogie frame transfer matrix,and the effective grasp of its condition number ensures the good characteristics of the transfer matrix,and then effectively controls the load identification error.Through the line test,data collection and analysis of each load system,the dynamic stress predicted by the measured load and the measured dynamic stress are compared,and the effectiveness of the frame load decoupling identification method is verified theoretically.(4)Preparation of test load spectrum.Through statistical analysis of the test load and test dynamic stress data,the preparation of a random load spectrum that can cover the damage situation of the frame structure is the core of the research in this paper.Based on the random load spectrum,the phase relationships among the load systems are obtained through correlation studies,and a method of compiling the phase relationships of the load series The influence of each factor in the phase relationship preparation on the test load spectrum to correctly reflect the fatigue life of the frame under actual operating conditions is discussed.