Research On Vibration Fatigue Of Subway Antenna Beam Based On Three Interval Method

As an important public transport,the subway has been attached great importance to its stability and safety.The antenna beam of the subway is a structure carrying Automatic Train Protection(ATP)antenna.It is installed at the end of the bogie frame and stimulated by vibration excitation from the end of the frame during subway running.When the excitation frequency of the antenna beam is close to its natural frequency,the structure is prone to resonance,resulting in vibration fatigue damage.In the service of the subway,fatigue cracks occur frequently in antenna beams,which affects the safety of train operation.Therefore,the vibration fatigue research of the antenna beam has important engineering significance.In this thesis,the vibration fatigue of the antenna beam is studied based on the three-interval method.The main contents are as follows:1、The finite element model of antenna beam is established,and the harmonic response analysis of the structure is carried out based on the modal superposition method to determine the resonance characteristics of the structure.The calculation results show that the first four natural frequencies of the antenna beam are the most sensitive,and they are prone to resonance excited by external loads.2、Based on the three-interval method,the acceleration power spectrum in standard IEC61373 is applied to the antenna beam for random vibration fatigue analysis.At the same time,the fatigue damage of the base metal and the main weld is calculated by combining the S-N curve and the linear fatigue accumulation criterion.The simulation results show that the vibration fatigue damage of antenna beam is mainly caused by vertical and lateral acceleration excitation,and the fatigue damage caused by longitudinal excitation is small.The fatigue damage value of the outer weld of the antenna hanger and the circular tube beam is large,which is consistent with the position of the fatigue crack in the actual operation.3、The Fourier transform is used to convert the acceleration of the antenna beam in actual operation into the acceleration power spectrum,and applied to the antenna beam for vibration fatigue analysis.By comparing the spectrum of the maximum stress under the measured excitation and the standard excitation,it can be seen that the natural frequencies of the structure excited by the two acceleration power spectra are consistent.The standard excitation has universal applicability and can effectively analyze the vibration characteristics and fatigue damage of antenna beam.At the same time,the overall fatigue damage value of the structure under the measured excitation is small.4、Based on the size optimization theory,the optimization software is used to optimize the structure of antenna beam.The vibration amplitude of the antenna beam under vertical excitation is reduced by changing the wall thickness of the beam tube from 6.3 mm to 9.5mm.Thus,the fatigue damage value of the outer welding seam of the antenna hanger and the beam tube is reduced by 61.2 %,which provides a reference for the reasonable design of the antenna beam.