| At present,the design and evaluation of the bogie frame of rail vehicles adopts international common technical standards and specifications in China.From the model design of the product to the mass production,it is necessary to pass three stages of fatigue reliability assessment,such as simulation calculation,fatigue reliability test verification,and line type test at the initial stage of operation.However,the actual use shows that after a period of use,there will still be a large area of fatigue reliability,and even some cracks appear locally.This reflects the fact that internationally strength technical standards and specifications cannot cover the full operating conditions of domestic vehicles.The load spectrum of the bogie frame is the key basis for the reliability design and fatigue test evaluation of the frame.This thesis adopts the direct test independent load technology by constructing the basic load system of the framework,and based on high-precision calibration method and testing technology,the load-time history and dynamic stress data of key parts under typical operating conditions are obtained.Finally,a high-precision discrete load spectrum was established to guide the structural design and reliability improvement,and based on the load mode,a multi-channel co-loading bench test spectrum is established,the test spectrum can cover structural damage under practical and complicated operating conditions and can be used for fatigue reliability test verification.A framework reliability life prediction model was established for life prediction and guidance for product repair and replacement,the main research contents of this thesis are as follows:(1)In this thesis,a high-precision force measuring frame and a test system are built,and the load test plan is determined.The load characteristic analysis and spectrum establishment require the separation of working conditions,and the segmentation and extraction of the measured load waveform are completed,and the characteristic statistics of each load are calculated and analyzed in the time domain and the frequency domain respectively.(2)Based on the principle of damage consistency,this thesis uses the least squares method,penalty function method,genetic algorithm,simulated annealing algorithm and improved tabu search algorithm to optimize the global optimization.Finally,the improved tabu search algorithm is used to establish the calibration load spectrum and calibration.The damage caused by the load spectrum can completely cover the measured damage of the line,and the damage ratio of large stress measuring points can be controlled between 1 and 2.2.The accuracy of the calculation results is much higher than the other four optimization algorithms.(3)In this thesis,based on the calibration load spectrum as the load input condition,the structural improvement of the frame is carried out.According to the stress distribution characteristics,the improvement scheme is improved successively,and the final improvement scheme is determined after the simulation calculation and verification.In order to facilitate the designer to carry out the frame anti-fatigue design,the vehicle system is proposed.A method of calculating the load factor value for each design parameter.(4)In order to shorten the cycle of fatigue reliability test and reflect the actual service conditions of the frame,this thesis proposes a complex multi-channel cooperative loading bench test spectrum based on load mode.According to the actual load and the actual equivalent stress,the nonlinear optimization model is built to optimize the load by introducing amplitude modulation and frequency modulation parameters and using the constraint criterion of damage as the constraint.The model is based on deep learning,greedy algorithm and Python programming environment.After optimization,the bench test spectrum the amplitude of the variation,the equal-frequency can cover the measured equivalent stress of all the points.The test plan can fully reflect the actual loading condition of the frame,and the simulation accuracy is high,which verifies the feasibility of the bench test plan.(5)By analyzing the fatigue damage of the frame,based on the stress-strength interference theory and the fatigue reliability model,the life prediction model of the key stress measurement point is established to predict the life of the frame,and the life distribution function and reliability curve and remaining life distribution curve of the fatigue weak point are obtained,this thesis guides the repair and replacement of the structure by predicting the remaining life of the frame stress measurement points.This research has made a breakthrough in the establishment of the load spectrum of urban rail vehicles for operating conditions,and provides a theoretical basis for establishing the reliability design and evaluation standards for the steering frame of urban rail vehicles in China.and it has a good theoretical guiding significance for comprehensively improving the design level of urban rail vehicles in China.and it has a high engineering application value to meet the construction of urban rail transit in China and in line with China’s "going out" strategy.99 Figure,32 table,82 reference. |
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