Research On The Force-measuring Bolster And The Force-measuring Carrying-saddles Of The 30-ton Axle Load Freight Car

The heavy haulage,due to its distinctive characteristics of large capacity,high efficiency and low cost,has become an important trend of the development of railway freight transportation.In order to meet the demands of the domestic freight transportation,the 30-ton axle load open wagon exclusive for the coal transportation has been successfully developed.In 2004,the first 30-ton axle load 20000-ton heavy haul freight car in China has been operated in Shuo-Huang line.As the principal load-carrying members of the freight car,the bolster as well as the carrying-saddles is usually under complex alternating loads such as the tension,the compression,the impact,the bending moment and so on,which all together result in the fatigue failure on a frequent basis.The main evidence on which the fatigue test of the freight bogie is carried out at present in china is the standard of TB1959" The static load and fatigue testing of the railway truck bolster and side frame ",a standard which was established referring to the AAR standard and yet could not perfectly reflect the actual domestic road conditions.Therefore the research and the design of the force-measuring bolster and the force-measuring carrying-saddl-es of the 30-ton axle load freight car is of great significance to the test and compilation of the load spectrum,and then to the fatigue assessment and the fatigue design of the heavy haul freight bogies.This paper designed the basic structures of the force-measuring bolster and the force-measuring carrying-saddles of the 30-ton axle load freight car,researched on the load identification method on the freight bogie based on the quasi-static deformation pattern,established the load coupling models respectively corresponding to the members of the bogie and finally verifying the fatigue strength of the force-measuring bolster and the force-measuring carrying-saddles given the increase of the axle load based on the Daqin load spectrum of the 25-ton axle load freight car.The main content of the paper is as follows:(1)The fatigue strength of the structure of the 30-ton axle load freight car bolster was verified and the modification plan was decided for this original structure.Based on the direct force-measuring method,the bolster was redesigned with the consideration of the size of the sensors for the purpose of turning it into a force-measuring bolster.The finite element analysis of the carrying-saddles was made,so were some local modifications to change it into a force-measuring sensor.Through the modification of the local structures was strenghened the structural strength of the bolster and were meanwhile accomplished the design of the load-measuring bolster and the load-measuring carrying-saddles.(2)The finite element analysis was made both on the force-measuring bolster and the force-measuring carrying-saddles,based on the result of which the structural strength was checked according to the AAR fatigue testing assessment standards.According the verification results,the structural strength of these two components both satisfy the fatigue design requirement.The weak points on the force-measuring bolster and the force-measuring carrying-saddles were presented and the corresponding load-stress converting factors were calculated,which were prepared for the application of the nominal stress method.(3)The quasi-static load measuring approach was applied and the low coupling load identification points were decided.The combination bridge way was designed and the load coupling models were formed.The condition number of each load-stress converting factor matrix was calculated to analyze the error of the reverse calculation of the loads.The results represented that these load-stress converting factor matrixes were not ill-conditioned matrixes,which means the error would be relatively small while these matrixes were used to calculate loads.(4)The force-measuring carrying-saddles was calibrated on the calibration test bed and the calibration lines were fitted based on the experiment results which was compared to the simulation calibration results.The difference between these two results was smaller than 10%,therefore the simulation calibration method is acceptable within the particular error ranges.(5)The fatigue life of the force-measuring bolster and the force-measuring carrying-saddles under different effective stress concentration factors was predicted with the method of nominal stress method and the Miner linear damage accumulation rule with the consideration of axle load increase based on the Daqin spectrum tested on the 25-ton axle load freight car.The results showed that the fatigue life of these two components were both longer than 6.25 million kms,which is the fatigue design requirement.