Load Characteristic And Strain Field Identification Method Of High-Speed Train Gearbox

With the greatly improved running speed,the reliability and safety of train operation have been widely concerned.As an important part of the high-speed train transmission system,the gearbox transfers the torque load of the motor to the axle through the meshing action of the gears,thus realizing the traction and braking function of the train.The gearbox has a complicated structure and its service conditions are poor.It has experienced fatigue damage many times during the operation of the line,which reduces the safety of train operation.The gearbox is mainly subjected to the motor torque load,the wheel-rail excitation load and the gear meshing load,the multiple loads are coupled with each other to cause the dynamic response of the box to be complex.The influence of each load on the dynamic response of the gearbox is analyzed by a suitable method.Identifying the overall dynamic response field of the structure has important research significance for gearbox design and structural strength assessment.In order to analyze the gearbox load characteristics and identify the dynamic response field of the gearbox,a force-measuring C-bracket identification gearbox load method with double strain gauge bridge method is proposed.The load applied to the gearbox is the rotary excitation load in the process of variable speed,modal frequencies and structural excitation orders are invariant in frequency domain and order domain,respectively.Modal parameters and structural excitation orders are identified by velocity-frequency domain method and velocity-order method,respectively.Recognition of the whole dynamic response field of a structure is realized by inversely calculating the intermediate-modal participation factor of the structural vibration through the dynamic response of the finite measured points on the surface of the structure.The main research work of the thesis is as follows:1.For the problem that the torque load of the gearbox motor is not easy to measure and the zero drift of the trend load is difficult to remove,a load-sensitive temperature-insensitive double strain gauge bridge force-measuring C-bracket is designed to identify the vertical load of the gearbox.The vertical loads of gearbox are decomposed into trend loads and vibration loads.Based on the power frequency electromagnetic strain signals and motor torque,and combined with the time domain characteristics of train speed signals,the effects of typical working conditions including acceleration and deceleration,tunnel crossing on trend loads and vibration loads are analyzed.The influence of two types gearboxes and train routing on trend load and vibration load is analyzed.A non-parametric estimation method based on two-dimensional nuclear density is proposed to estimate vertical load of gearbox.The methods of mileage extrapolation and quantile extrapolation are used for extrapolating vertical load of gearbox.Torque load load spectra and different quantiles load spectra are obtained by extrapolated load and load calibration coefficient.2.The modal parameters of gearbox directly determine the dynamic behavior of train transmission system.The modal parameters are identified by using the least square complex frequency domain method based on the finite vibration acceleration measure points of gearbox under on-line operation conditions.The velocity-frequency domain method is used to identify modal frequencies based on the fact that the vibration response does not vary with the velocity at the modal frequencies of structures.The frequency band of modes with small vibration energy is analyzed by the zoom spectrum method,and the correlation of identified modes is analyzed by the MAC value method of modal judgment criterion,and the causes of false modes are explained.The relationship between experimental value and validated value is compared by modal synthesis method to verify the identification results of modal parameters.3.There is a fixed linear relationship between the vibration response frequency and the rotating speed of the rotating part structure during the variable speed process.Time-domain vibration response is transformed into angle-domain signal by using order tracking technique of quadratic curve order ratio.Velocity-order method is used to obtain the order tracking waterfall diagram.Peak search method and zoom spectrum method are combined to identify the order of gear meshing excitation,meshing harmonic excitation,motor harmonic torque excitation and wheel-rail excitation.The response of the structural excitation source is obtained by analyzing the order domain amplitude spectrum of the identified structural excitation.The time domain characteristics of the harmonic torque excitation,wheel-rail excitation and gear meshing excitation of the motor are analyzed by the order filter method.Coherence analysis method is used to analyze the correlation of structural excitation response.Combining with the amplitude spectrum analysis,time domain response analysis and coherence analysis of structural excitation,the vibration transmission path of structural excitation is given.This method provides the theoretical basis for the study of structural dynamics and structural dynamic response of gearbox of high-speed train.4.Reverse calculation of structural vibration intermediate-modal participation factor identifies the overall dynamic response of the structure,and optimizes the strain Measure points of the measurable parts on the surface of the structure.The mode matrix of strain mode and the decoupling equation of strain response and modal participation factor are deduced,and the estimation formula of modal participation factor under modal truncation is given.The optimum location and direction of measuring points are optimized by using D optimal design theory,and the optimum number of measuring points is obtained by optimizing the condition number of weighted modal strain matrix.The sensitivity of the optimized set of Measure points to all modes is analyzed,and the modal participation factor is estimated by the least square method.Taking cantilever beam as an experiment,the feasibility of the method proposed in this paper for identifying modal participation factors is verified.This method provides a new method for dynamic response test analysis of complex structures which cannot be directly tested.5.Aiming at the problem that the dynamic strain response of the internal structure of the gearbox can not be obtained by the direct test method or the quasi-static calibration method under the condition of line operation,the force characteristics of the gearbox are analyzed,and the number,location and direction of measuring points are optimized.The transient dynamics method and steady-state dynamics method are used to analyze the time and frequency domain dynamic characteristics of the gearbox respectively.The time domain and frequency domain dynamic responses are processed by error respectively,and the modal participation factor is identified according to the erroneous dynamic responses.The correlation between identification modal participation factor and theoretical modal participation factor,waveform coincidence degree and the influence of modal participation factor on overall vibration are analyzed.Based on the modal superposition method,the strain response of structures in time domain and frequency domain is analyzed and identified,and compared with the theoretical strain response of structures.The accuracy of identifying the overall dynamic response of the box structure by the modal participation factor identification method proposed in this paper is verified.