Fatigue Performance And Residual Life Evaluation Of Welded Bogie Frame Made Of Casting Materials For Railway Passenger Vehicle

By the end of 2019,the total length of China’s railways has reached 139,000 kilometers(including about 35,000 km high-speed railway),which is second only to the United States of America(about 220,000 kilometers).With the development of world economy and the recovery of industry,the economic cycle of rail transit industry is in a new rising stage.At present,driven by various favorable policies of the state,and on the premise of stabilizing the existing domestic market,China’s rail transit industry has implemented the national "going global" development strategy and actively seized the international market.Bogie is an important component of railway vehicle,which supports the car body and forces the vehicle to move along the track.As the basic component of bogie,the bogie frame’s performance directly affects the running quality and driving safety of railway vehicles.Therefore,the primary goal of bogie frame strength design is the structural safety.In this thesis,the welded bogie frame of a new type of exported passenger car is taken as the object,and the main works are as follows:A series of tests on microstructure and mechanical properties were carried out on the G20Mn5 cast steel and its welded joints for the bogie frame,including metallographic observation,hardness test,tensile test,high cycle fatigue test,low cycle fatigue test,crack growth rate and threshold value test,SEM observation and non-destructive test.Very comprehensive material parameters of G20Mn5 cast steel were obtained.The three-dimensional CAD model of welded bogie frame is meshed into hexahedral solid elements.The finite element model of bogie frame is simulated and analyzed under 15 operating load conditions and 7 abnormal load conditions in accordance with UIC 515-4standard and EN 13749 standard.The static strength of bogie frame is evaluated on the basis of the 4th strength theory,and Goodman fatigue limit diagram is drawn to assess the fatigue strength.Then,the fatigue life of critical regions of the bogie frame are evaluated based on Miner’s fatigue cumulative damage criterion and the measured load spectrum.The assessment results point out that the static strength and fatigue strength of bogie frame satisfy the design requirements,and the fatigue life of all critical regions meets the 30-year service requirements of the bogie frame.Finally,based on the measured brake load spectrum and combined with the defect regularization method,different depth cracks are implanted in the welding heat affected zone between the brake shoe hanger and the crossbeam.Combined with the Paris crack growth model and the test data,the residual fatigue life of the brake shoe hanger is calculated by the damage tolerance method.The calculation results show that the casting defects less than 0.5mm in the welding heat affected zone between the brake shoe hanger and the crossbeam will not expand;If the crack propagates from 1 mm to 14 mm,the bogie frame needs to work70.98 million kilometers theoretically,this can fully meet the design requirements of fatigue life and has a sufficient safety margin.